Eidetic -- First choice would be AF. I like the idea of leaving the US at such a time that I get to Europe in the evening -- it is easier for me to adjust. It is hard to get an upgrade seat on the AF sometimes (as it was on SR), so the next preference is the CVG DL flight (this is my return route this time). DL Systemwide upgrades rule!
I've taken LH in Business (wonderful) and coach (living hell). SFO being United City for FF, this flight is always packed. Last flight that wendolene & I took together SFO-FRA in LH business: The flight attendents talked to me in English, to her in German (don't know how they figured out she was fluent & I was wasn't) -- by the end of the flight, they were coming over to her for advice on how to say certain things in English! Loved the lounge in Frankfurt, too.
But I paid for that flight out of my own pocket. Most of my travel is business, and my company usually only pays for coach unless it is a super-long trip, and then only after getting everyone just about up to the CEO to sign off on it. So I crave those upgrades, and I'm almost 100% successful at getting them with DL or its codeshares.