I'm sure you'll get opinions on both sides of this but I researched this quite a bit last year. Bottom line is this....if your floor doesn't have a polyethylene vapor barrier under it, it is likely that whatever you put on top is going to get pushed off (from underneath) by the moisture.....IMO. That said, I went with the cheap Home Depot Behr epoxy stuff and a year later, it's held up better than I thought it would.
It is starting to flake a bit in the traffic areas too. In hindsight, I would have just put down a thick vapor barrier on top of the concrete and put one of those 'dry fit' jigsaw tile floors on top.
