I would avoid the super-cheapie knock-offs. I bought a pair from Walmart
just to try them out. Soooo not the same. And they aren't the most attractive shoes to begin with, so why get something that's not as comfy or durable??? A lot of kids at dd's school seem to wear the Airwalks, and they seem to hold up well (I see them wearing the same pair most of the year), and they come in cool swirly color patterns, but I haven't actually tried them on.
The sizing is the one thing I take issue with. When dd first got hers, one size was too small, and the next was too large. Ds and I have never had that problem though, so maybe it's just person by person. At least try some on.
Interesting thing, ds tends to shuffle his feet when he walks, and wears the tread off the heels of every single pair of shoes. His crocs look scuffed, but don't seem to be any less slip resistant. I don't think they became any less comfortable either, because he has that worn blue pair and a newer black pair....and he'll pick the blues ones every time, given a choice. (he also picked out both pairs, so he liked both colors once upon a time)