Is it possible that I'm the only one who's done both of these planes in business in the last year? I think I should get an FT Merit Badge My 748 experience was FRA-LAX on the upper deck. For Envoy, PHL-LHR-PHL once in a plane with a crew rest compartment up front and once in the version with a crew rest seat. The difference between the two A330 versions is not something you'll notice.

My take on the two is that the hard product is roughly equal. The Envoy seat will be significantly more private if that's important to you. The LH seat is pretty open and reminds me more of a slightly bigger, spiffier version of UA's new J. I'm 6'5" and the LH seat seemed like a better fit, length-wise for me than Envoy. Entertainment was typical inflight movies on both airlines, though by the end of the year I'd seen most of what US was offering.

In terms of soft product, I had a pretty good experience with service both on US. It is definitely more casual than LH, but I found LH's FA's to be a bit stern/harsh. That's probably more a function of the culture clash between SoCal and Germany than anything else.

If found LH food to be quite bland and a bit of a let down. The US food was nothing special, but given the choice I'd eat the Envoy meal. Where the two airlines diverge is in the relative quality of their wine selections. LH wins this hands down... not even close.

When I flew the 748, it didn't have FlyNet or it wasn't working.

How I'd decide?
1) If internet is a must have or you're a wine drinker, take LH. (assuming FlyNet is operational)
2) If you value more privacy and prefer a more casual service, take US.
3) Flight length - for going EU to west coast (or vv), I'd take LH because I know I can eat, have a drink, catch a movie, and still get some sleep. The US flights, especially PHL-EU are too short for anything other than dining and drinks/movies.
4) Airline food is airline food. It's almost never notable to me in business.

Remember also that Frankfurt is a big place and you have a good chance of winding up on a bus to/from a connection. It'll take longer than you think to get where you're going.