Wow! You guys are great, thanks for all the replies (especially 2_Many_Miles lots of good info

)
I've flown AA 2 times this Spring (ORD-MIA, ORD-YUL) in coach, I was impressed by the space and the service was fairly good. However, I have been flying UA since I was 10, so I am a little partial to them. So it really comes down to a tough decision, between AA and UA I think I'm leaning towards joining AA.
Although, I'm still seriously considering CO or NW since I'd prefer to be able to fly business or first as much as possible. In terms of routing, most of my clients will be in the USA with a few internationally. I think most of the big domestic carriers should serve me pretty well.
Again, thanks for all the info folks. Is there any hotel program that stands out from the others?
Regards,
Gene