Actually LHR-ATL on VS has consistently been on the A350 (and is still showing A350 through mid-July) which I'd argue is a better seat than the DL 767s, although there's no bar on the A350 and only a kinda odd lounge setup that largely remains unused.

So personally if it's still showing A350 on the dates I'm flying (and not the A330 or 787) I'd try to switch to VS, but of course if that's not possible DL is perfectly fine as well