Well, I think for *A, I will just stick to United. Seems like there are some United flights in and out of Taipei (my main hub), and Singapore's program doesn't look too attractive.

Yeah, seems like there are upgrades given on AA and JL once you reach top tier status, and basically none on Cathay. I have been bumped from economy to business once just because I flew them quite often in a span of a month, not sure if that's occurs often or not. I'll have to think about... but thanks for everyone's input!