If CamperX is user / community based, then it depends on the target user I guess.
I'd imagine HEMA don't go out scouting great campsites, so most likely users feed the database and it builds, like Wikicamps.
That being the case, you might likely see better quality sites listed on CamperX (OVER TIME) as most of those users will be more Aussie 4wd type travellers ?
Wiki has a very high % of overseas backpackers etc, and many highway sites can be quite unsightly gravel pits and such.
That said, if you read between the lines with Wiki, you can usually sift through those fairly easily, who wants to camp within 100m of a major highway anyway ?
Wiki has been going a long time, so the database of camps (text info and images too) is quite huge.
It might also come down to what the "the CAMPERX premium map subscription" costs, it sounds like an ongoing annual fee ?