I've got both, and as far as I can tell, the only difference is Concealex is smoother and glossier and maybe (MAYBE) slightly thinner. I have trouble getting the fine dust out of the surface texture of the Kydex.
As for the UCH - it's naturally really slow if you tuck your shirt over it (you can also tuck your shirt under it - I like having the choice). When the shirt is tucked over it, you only see a black plastic rectangle on the belt.
