I'd take the non-stop... no compelling reason for a connection here.
That said, I'm apparently one of the few who doesn't mind LHR. Maybe I've been lucky, but my T3 to T5 connections (or the reverse) are generally efficient (ok, LHR-efficient), and on the return, the CX lounge is great (and looking forward to trying out Qantas). Sure, the bus and security checks are annoying (along with a few gates which are miles away), but I'm generally from plane to lounge in the other terminal in 30-40 mins.