I can't speak for SFO specifically, as I'm not based there. I do know it is one of the more junior bases, so you should move up relatively quickly. Since I've been here, there are always 737 openings there and in EWR.

I don't know the breakdown of the 737 vs Airbus out there, but if it's anything like my base, there are more than twice as many people on the 737. There are also a lot more 737's coming in the near future compared to the Airbus. Having flown both, the cockpit of the Airbus is nicer and quieter than the NG's, but the MAX is probably about as quiet as the Airbus.

I have no ideas what there trips are like, but I would assume the typical mix of 1, 2, 3, and 4 day trips. I know the 737 does a lot of Hawaii flying, while the Airbus doesn't do any. I would also assume there are a good number of trips on both planes that start with East Coast red-eyes, but I don't know for sure.