I’ve flown business (BA) a few times, paid for from my own pocket (with money, not airmiles or anything), and absolutely would again. 6foot beds alone are worth it on a 9hr+ flight
The whole experience of flying, from the moment you arrive at the airport, is miles better (I like flying/planes, despise airports).
Not sure I’d pay the extra for first, yes you get nicer wines and food, a nicer, more luxurious lounge, but I’m not sure that means that much to me, over business.