Hi;

I flew the SFO-CDG route for about 5 years, and on that 747. I switched over to Star Alliance because I was able to get into the lounges here in Europe from Lufthansa which are still a step above. The problem with AF was that their planes and staff just got old and tired. But now United is a horrible airline in my opinion, and I would recommend to avoid it on International flights.

If you book the voyager, you are upstairs on the 747, which is much better than down. All this assumes you are flying economy and need to get to CDG. If you just need to get into Europe from SFO I recommend SFO to Munich on Lufthansa.