It's an individual choice. I "grew" up with American, i.e. I was forced to fly it when I started working as a consultant at age 23. Now I'm 27 and have been EXP for the past 4 years. I'm all AA till I die or till they file for bankruptcy, which will likely happen first. AA works extremely well for me, I love their 8 SWU and the fact that any international fare is upgradeable. I'm sure UA would have been as great a program for me if I started off with them 4 years ago.