Personally I'd go for LHR. Several reasons: I prefer the 777 and swear the bed is wider at the knees, though the A350 has more total leg space. Screen resolution vastly superior on A350.

That said, I am not that big fan I've decided of either the 350 or 787 as they are too quiet, and if there's going to be noise I prefer that to largely be engine rather than engine plus people noise.

Whilst I live by Victoria station, I often prefer LHR, especially if using car or can use the tube. Arriving to Victoria is actually not that convenient for Hyde Park Corner given you still need to get a cab or walk a fair distance.

If maximising J matters then you also have the arrivals lounge as pointed out. Assuming you're staying a hotel, that's not a bad option given the arrival time.