Pick based on schedule first and foremost. Not sure when OP is traveling, but currently the nighttime SFO-HKG is a 77W/773 (whereas the daytime SFO-HKG is a 772), so they might be comparing between a nighttime SFO-HKG and a daytime LAX-HKG, which are, dare I say, as different as night and day.

If schedules are roughly similar, there aren't any fatal flaws to one option (e.g., uncomfortably short SFO connection), and OP is picking purely based on aircraft type; then I'd pick the SFO connection.