I'd agree that C aenus are most common. I got a bronze one first and she has produced lots of kids for me, which I have sold to my LPS and others. I was surprised that the LPS I sold them to seemed unfamiliar with the species, but said the albinos were so common they don't pay much for them. When I brought them in people were oohing and aaahing over how pretty and cute they were and saying thay'd never seen that kind before. At another store I was told that the albinos are very common , but that the "species" or "natural" color are harder to find, and they looked forward to getting some of mine.
I also see peppered corries pretty commonly but maybe a bout a dollar more expensive, and I've seen lots of pandas and "spotted", which could be C julii or shwartzi, which I'm pretty sure one of mine is, or thay can be some other species. somebody had a post with a link a while back with pictures of lots of different ones.