I usually do SFO for 3-5 day trips and I've found it better to always take the BA287 outbound for several reasons;
1. I got to get to LHR from GLA, no need for 5am start
2. It arrives after KL, VS, AF, CX(?) & BA285, so SFO immigration generally quiet
3. Less time needed to stay awake on arrival, I generally stay downtown or in local area, so washed and out for light dinner by 7:30pm.

Inbound to LHR, always the BA285
1. Avoids the same outbounds as mentioned above, so airport is quieter
2. Closer to sleeping time after the meal is served, so easier to sleep (as you would want to on a night flight)
3. FCC usually quieter in LHR early afternoon (in my expereince)
4. Connex up to GLA, home late afternoon, less time to stay awake until bedtime

All told, a less stressful trip and it works out better for minimising jetlag which is paramount^