They are both quite expensive now, but fairly similar ... others have spread out the details, so no need for to expand on that. I am a member of both but use them for 'emergencies' only ... I prefer small sites, so CS/CL where found. I usually use them if it is my first time in an area and I want to explore other possible parking places, so they get a night out of me. What I dislike intensely is the enforced booking of multiple nights. I suppose most of my reason for being a member is that I can get water, toilet disposal and a proper shower when I need them. My van is off-grid capable, so I object to be charged for electrical hookup which I do not need.
Most of my nights are spent in places which welcome motorhomes and charge little or nothing because we support the local area being visited. Pubs are great and I do like eating out if its decent food. Supermarket carparks are possible, but do buy at least a bag of shopping and ASK the manager! I have used rest areas when covering a distance and just want a four hour head-down. In Scotland, some carparks in smaller towns allow motorhomes to park up for free ... Jedburgh which is about an hour south of Edinburgh is a beautiful small historic town well worth a visit, which I regularly use for overnight stops, just pull into the free large carpark ... again its nice to spend some cash locally !