I've lived in China for 20 yrs (3 in HK and 17 in Shanghai). I'd never go back to the UK unless the air here becomes so bad that it's not an option (at the moment Shanghai, on average, is probably no worse than London, it's the North of China where the air is horrendous, and gets blown down here when the prevailing winds are from the N, NE). The quality of life for an expat is just so much higher here.
To call it 'quite' modern is a massive understatement - 3 of the world's top 10 highest buildings within 1/2 mile for example, 2 huge modern airports, the largest Metro system in the world (and it's very clean and very good) - as of 2014 - and still growing at an unprecedented rate, it'll be twice the size of the 2nd largest, London, within 20 years, the fastest, sleekest and sexiest high speed train network in the world, including Japan, huge numbers of top class restaurants, massive shopping malls selling huge amounts of luxury goods (China being set to become the top market this year), top sales market for Jaguar, Ferrari, Mercedes, BMW etc. outside of their home countries ... and so on and so on).
It's damn expensive here now though (e.g. imported foodstuff 2-3 times costlier than Waitroses in Canary Wharf (my benchmark as that's where my daughter lives), cars cost 2-3 times those in the USA (same model) plus US$15,000 for your numberplate etc.).