Definitely go on United.

US airways product is tired and old and meal service is sub standard (presentation is like your grandma's kitchen). Not to mention employee morale is extremely low currently.

If you fly a UA wide body (777 or 747), you get the First Class Suites which essentially is a bed! And if you fly premium transcon (jfk to sfo/lax) you get to try the flat beds on the P.S. (sm) service.

For the price you pay for a F ticket, you are better off on United. Domestically I think they are quite similar but international service, United is miles ahead anyday!