I have used them for a tent and motorhome. I didn't feel looked down on for being in a tent, but it does depend on what you want.
For us, we like having the showers/toilets rather than using them in our motorhome. The sites can be a bit out of the way for local shops etc, so we deliberately look for ones near a town centre. The discounts on prices are not too bad, plus you get discounts on insurance, ferry travel and places like Go Outdoors. We only joined last year, but will likely renew for next. I have heard lots of complaints about the caravan and motorhome club, so probably won't join that one.
We have been to several across the country and have always been impressed by the cleanliness and quiet, although you have to remember when they close the facilities for cleaning as we have been caught out a couple of times.