I prefer SQ mostly because I am on a relatively short connection and want the shower. They are typically empty and (especially when they opened) the showers are great. Food is decent and at one time they had proper champagne.

Of the 25 times I have transited - I have been to the UA lounge only once but have to say it had the best bar and I would like to explore it more again on the next trip. Last few trips via LHR were during C-19 so all lounges were actually closed.