They have lots of options (fast/slow/sleeper/premium/etc..): https://www.travelchinaguide.com/china-trains/display.aspx?t... and also pricing is more predictable. In general, it's only a bit cheaper than flying but China rail stations are usually in the center of their cities, so you save 30minx2 vs the airport.
in beijing and in changsha the primary high speed railway stations are almost as far out from the city as the airports. shanghai is also at one of the airport (the one that is closer to the city at least). i believe several other cities are similar. the problem is that chinese cities are huge, so looking at the map it feels like the trainstations are in the city, but then the same is true for many airports.