The main thing about LHR-LAX routing is that westbound seems to generally go well north of the Great Circle, typically crossing Baffin Island, while eastbound is often well south of The Circle. This is presumably due to prevailing winds. Yes, westbound is generally longer. I've actually passed overhead Montreal eastbound, while (to keep on thread) in a TWA 747-100 once we made a refuelling stop eastbound very far south, at Bangor ME.