If the LHR lounge is one of the factors, keep in mind that flying in CW it is 'only' Galleries Club access you get.

I say 'only' simply to differentiate from Galleries First and the CCR. Galleries Club is a very nice lounge.

And I mention this to point out that unless you are doing Pre-Flight Dininig on a sleeper flight etc, you can experience exactly the same Galleries Club lounge at LHR on a cheap CE return.

Yes the onboard product will be a bit different between CW and CW-LCY, but I think I'd do CW-LCY for the other aspects of the inflight experince being more interesting.

However, I'm not really a long haul person so thouse are just my thoughts.... and I've not done CW-LCY so can't comment on how it compares.