The two main clubs are similar in the standard of their sites, but there are differences, and your either/or choice might be influenced by the differences. This summary (from our 3 year experience) is generalist - there are site exceptions!
Caravan & Motorhome Club:
Mostly caravans and larger motorhomes. As a result, most sites have 100% hard standing pitches, which are usually reasonably level. The overall site are is usually compact (space efficient!), and the pitches lined up around the access roads. The sites can look quite ‘vanilla’
The demographic is very much skewed towards older couples. We are in our 60’s and often we’ve been the youngest campers in our row.
The facilities are always (?) a good standard, all very similar, and always clean. A bit like McDonalds, you know what you’re going to get!
Pitch costs have risen fairy significantly over the past 2 years, so now a night away in low season for 2 people will be around £35 to £40 and in high season, around £40 to £55. Annual membership is a little more than CCC - It used to be the same.
Pitch selection is your choice. Drive around to look for the one that suits you, then tell the site team. You should put a sign out if you leave during the day. There are ‘black and white’ rules on how to position your van given that the spacing between pitches isn’t huge, and fire protection etc.
Camping & Caravanning Club:
Mixture of caravans, motorhomes, campervans and tents. As there are more tents and smaller vans, there are generally more grass pitches, plus grass pitches without electric. The overall site area is usually larger - more space. Use Google maps to view the CCC and CAMC sites at Sandringham to illustrate.
The demographic is skewed towards families and younger couples (tenting etc).
The facilities are usually good, but we’ve had a couple of experiences which were borderline acceptable to my better half. I think the different age demographic with lots more kids had an effect on cleanliness.
The pitch costs are similar to CAMC, but CCC give more frequent discounts for things like out of season, grass pitches, older (over 60 members). We can get away in the low season for as little as £30 a night, with our age related discount. High season is around £5/ night cheaper than CAMC.
Pitch selection is made by the campsite managers, but on a couple of occasions we have called ahead to request two pitches together. As the area of the sites tend to be larger and less regimented into rows around roads, distance between pitches can be greater, or conversely you might find the odd pitch squeezed in between others.
Private Sites and other groups:
If you become a club member, don’t forget to look at the private sites, they can be as good / better than club sites. We have membership to both clubs, and also use private ones.
One handy feature of both clubs is the move to position sites in or close to major cities and towns, examples London, York, Bristol, Edinburgh. This gives lower cost accommodation when going to shows, concerts, or visiting people.
Hope this helps a bit.