Will be traveling in Business Class either from PHL or IAD to FRA in early September. Want to take advantage of the current offers out there for a free Economy ticket with the purchase of a Business Class ticket. Not sure if I will book US or UAL for the promo since they both have direct flights. Can anyone recommend what they would do?

I know UA offers more destinations, which I can use later with the free world wide ticket but the problem is that I would have to open a UAL FF account since I currently put all my Star Alliance miles on my LH Senator card. (Promo requires miles to be credited to UA to get free ticket!) With US I am more limited as to destinations they fly directly. Promo states that US voucher can be used on UAL as well but I think this will be harder to do.

Recommendations Please!

Many of the UA flights are now showing up as US codeshare, and that will probably expand into the future. With US also joining *A in the near future, I'd probably go with the US flight on the Airbus 330 (if possible, I'd rather have it and not the 767). One note from many of us that have flown through PHL -- plan for checked baggage to potentially get lost/delayed and have some stuff in a carry-on. They've had periodic major issues with the baggage system in PHL.