It's useful to read reviews from people who for the most part would not be reviewing rail services. They've also tackled the Caledonian Sleeper:
https://www.headforpoints.com/2024/01/29/review-caledonan-sleeper-train-club-room/I've travelled on neither since they've been renewed, but at least from the photos, in terms of restful ambience and design quality,
GWR▸ wins this hands down.
(The Caledonian sleeper, travelling in 2015 and 2018, treated us to an unpowered lounge car on a winter run to Fort William, and then in 2018 to Inverness, the cabin blind was permanently jammed shut. The previous trip was some time earlier on the Anglo-Scottish West Country sleeper - both directions - and that was just fine... must have slept well as we left Waverley and climbed Arthurs Seat then came down for breakfast...)
Mark