In both Europe and Japan, the trains (Shinkansen, ICE, Thalys, TGV, etc.) are usually a better bet in my experience just due to convenience of centrally-located train stations and the absence of the "security theater" and other hassles and delays associated with airports. In addition, the scenery of the routes I have been across has been a big plus. The only downside is the environmental control, or occasional lack thereof, with incredibly high humidity in Japan, and cars that are too hot or too cold in Europe.

The Korean versions haven't been as easy to use, and the scenery is not worth the effort, but again, for the distances traveled, it is a wash for avoiding airport hassle.

The mainland Chinese train infrastructure has been inconvenient enough to get to and use and that I probably won't do it more than my first three tries, for all the reasons mentioned above. You basically exchange one type of travel inconvenience for a different flavor of equal annoyance and delay.