I've never transited in (just terminated or departed) either so I can't offer help on that end but a couple things to consider.
UA's HND - SFO (which doesn't launch until October 26th - so keep that in mind depending on when you are booking for) is on a 787. NRT - SFO is on a 744.
I think most people would urge you to take NRT - SFO on ANA if possible. I believe it's on the 77W so it has the new business class and of course ANA service which is better than UA by leaps and bounds.