When selecting a region/city there are a number of differences to consider. These will help you make a better educated decision about the type of city that you would like to live & work in for your placement year.
Pollution (Recommended: South)
Pollution is still unfortunately a problem in China, although the issue has come a long way in the last 10 years as China strives to go more and more green. 3-year pollution averages across China are on the decline overall and in many cities the constant gray skies that once made the headlines around the world are slowly disappearing. That being said pollution may still affect your experience in China and may be one of the factors that determine the city/region that you choose to live in.
As a general rule of thumb, the more north you are the worse the pollution is likely to be where as the more south you go the more clear skies you are likely to encounter. This is for two main reasons. The first is that the north of China has a lot more heavy industry than that of its southern counterpart which may increase pollution in the area. The second is that the weather in the northern regions tends to be much colder in the winter months which causes pollution to linger in the air due to the density of the air causing more days with gray polluted skies. As it begins to get to become spring and the weather becomes more pleasant the pollution tends to decrease.
For more information about the pollution in different cities across China, have a look at the iqair website. On this website you can directly compare multiple Chinese cities in a single list including yearly averages, monthly averages, and you can even rank each city.
Climate (Recommended: Central/Eastern/South)
The climate of a city is a big factor for many when choosing the city that you want to live in. In the summer months the climate tends to be less of an issue as nearly all of the regions are considered to be hot (25c +), however in the winter months there can be large differences between the Northern, Central, & Southern regions.
The northern regions are known for having two distinct seasons. A bitterly cold winter (0 to -30c depending on the area) while having a hot summer (25-35c). The central/eastern regions have much more of a distinct 4 seasons with the winters being cold (+5 to -5c), the spring & summers being mild to warm (15-25c) and the summers being hot (25-40c). The southern regions are known for having a short mild winter that lasts around 3 to 4 months (10-20c) with the rest of the year being much hotter (20-40c).
To learn more about the differences in climate between cities/regions, you should use the timeanddate website. It has a tool that allows you to check historical averages as well as historical data from a given year to see how the weather was during a particular day/week/month.
Food (Recommended: All Regions!)
China is famous in the west for prawn crackers, sweet and sour pork balls, chicken chow mein, and spring rolls but these are actually very different from the types of food that you will actually find in China. Every region in China has its own specialist dishes (and even almost every city!). China has probably the most diverse and biggest food selection of any country on planet Earth. So much so that you could spend 20 years in China, and still not eat all of the food that it has to offer.
For spicy food you may like to live in Chongqing, Chengdu, or Hunan province. These three provinces have SUPER spicy food all day long. If you are looking at more simple and unique dishes then Guangdong province may be your preferred choice. If you are a person that prefers sweet food then you may be better suited in Shanghai which has a number of sweet dishes. If you are an admirer of roast duck you may enjoy living in Beijing.
Do know that while these cities/regions are famous for their dishes and may offer the tastiest version of their dishes available in China. These days you can find food from all around China in most cities (especially the bigger ones) meaning that where ever you are you can experience each regions specific food.
For food there is no better resource than YouTube. There are some amazing food channels on YouTube that showcase exactly what China has to offer. One that is particularly good is TheFoodRanger. This YouTube channel has many videos on the different specialities found within China (you can waste your entire day watching!)
Language Learning (Recommended: Beijing)
If your main focus for going to China is to improve you Chinese language skills then you may prefer to go to Beijing where the national language Mandarin originates from. Regions close to Beijing also tend to have closer accents to that of Mandarin also known in Chinese as putonghua. As you get into the southern regions of China you will find that there are much greater differences between the local dialects spoken which may make learning the standard mandarin more challenging.
That being said all people under the age of 60 should be able to speak mandarin as the language was introduced as the countries default language in the 1950's and is taught in all schools across China. However these local languages may affect the way people from each region pronounce words just like how people across the UK or US may have different pronunciations for words depending on where they are from.
Fun fact: There are still over 290 languages in existence in China today!
Types of Cities (Recommended: Tier 1/2 for those unsure, Tier 3 & 4 for adventures)
Compared with western countries all of the cities in China are big VERY BIG. Some of the cities that are regarded by locals to be small towns can have 1 million people living in them, while the largest cities Shanghai, Beijing, Shenzhen, & Guangzhou each have between 14 and 27 million people.
If you are a little bit worried about travelling to China and being alone in a foreign country that has a different culture, language, and food amongst other things then you may be better living in one of the tier 1 cities. Cities in China are unofficially ranked into tier systems to give you a better understanding of their development.
If you are looking to live a western life style in China then Shanghai is your safest option. If you are looking for a completely new experience then you may be better suited to live in a tier 3 or below city that will give you a completely new outlook on China and the life there. If you are somewhere in-between then living in a tier 1 or tier 2 city such as Beijing, Guangzhou, or Shenzhen may be a better fit for yourself. You can still experience China while having many of the comforts of home.
For more information:
You can find a list about the classified tier lists for cities here
Western Lifestyle (Recommended: Shanghai)
Shanghai is by far the most western city in China and if you choose to live in Shanghai you will have by far the easiest time of any of the cities in China. There is easy access to western restaurants & bars. Shanghai has by far the largest expat community in China making up around 30% of all of the foreigners in China. It also has the greatest range of coffee shops, craft beer bars, and western import shops available if you are missing something from home. After Shanghai comes Beijing & Guangzhou which also have a large expat community and many of the same things as Shanghai but to a lesser extent, and then followed by Shenzhen. While Shenzhen does have a bit less than the first three cities mentioned, it is only 20km away from Hong Kong which is by far the most westernised city in China. That means if you are living in Shenzhen you can easily go to Hong kong at the weekend (just 1 hour total time) to get that western life style.
Culture (Recommended: Beijing/Xi'an)
If culture is your biggest drive for going to China then you may be better suited to the northern regions of China (especially Beijing). The north of China contains much more of the old historical political and historical centres of China and will give you a feeling that is much closer to how China is often perceived in the media overseas. Here you can find things such as the Great Wall of China, the Forbidden palace, & the famous Hutongs in Beijing, the terracotta warriors in Xi'an.
That is not to say that other cities in China don't have their own amazing culture. There is a lot of culture to explore all across China, however if you are looking for the "China experience" how many westerners perceive China to be, then they are your best bets.
Cost of Living (Recommended a Tier 2 or below city)
The cost of living in China is generally MUCH CHEAPER than that of in your home country. Even in the biggest and most expensive cities (tier 1 cities) the cost of living can be less than half of that in the UK. This will however depend on the type of lifestyle that you live. If you live a Chinese lifestyle (eat Chinese food all day), shop like Chinese people do then you can live for around £300-400 a month very comfortably! If you want to still live your western lifestyle everyday then you may need a bit more money to get by as some imported products or products that are not frequently used by Chinese people i.e. milk & cheese can cost more money in China than in the west.
For more information:
A good website to use is numbeo which allows you to compare the cost of living in different cities around the world on typical expenses i.e. hotels and restaurants. Please do note that as this app is updated directly by user submitted data it is not always 100% accurate and may not be very accurate for comparing the cost between cities within China, but can still give you a good sense of the overall cost relative to your home country.
China is considered to be a safe country for living in. If you ask many foreigners that have lived in China they will tell you that China is safer than their home country for crime. The Chinese society puts a high emphasis on trust and you shouldn't be too worried about being involved in serious crime during your time in China. When you get to China you will notice a few things that may stand out. The first is that there are so many CCTV cameras everywhere. Really! everywhere! These are linked to the police station in the local communities that are watched to keep people safe on the streets. The second thing you will notice is just how many people are on the streets. Even if you go out at 11PM at night in China you can expect to see hundreds of people still walking on the street as many businesses in China don't even close until 10 or 11PM at night.
One thing that you may need to be aware of are scams specifically targeted at foreigners. As a foreigner in China you may be seen as an easy target for scams such as the tea house scam or art gallery scam. These scams are not something that you need to worry about in your daily life but if you go to major tourist hotspots you may come across them once or twice in your time in China. There is a simple and easy rule to follow. If something seems a little too good to be true, it probably is. You can simply tell the people that you appreciate their offer but you aren't interested and then just walk away. These scams are less common in China these days as the police in many cities have driven these types of scammers away, but they can still occur from time to time.
It is recommended that you check out the foreign travel advice issued by your state government before travelling to China. If you are in the UK you can check out the UK government travel advice website. If you are living in another country then please refer to your own government's advice.