I haven't done much F on US or CO since SEP so I can't consider the recent changes to food service, but I think the food and FAs are nicer on US than CO.
CO tends to pack their F class (I got tired of waiting at the gate until :10 before dp for an upgrade as a CO Platinum, so back to NW I went (for elite status and NW-metal)).
Competition for upgrades is less fierce on NW (probably since it isn't as nice).
------------------
Life's a banquet, and most poor suckers are starving to death! - Auntie Mame
http://www.angelfire.com/ny3/globalgourmets