We use 6" wheels, so I have experience with these AMs (
http://www.andymark.com/product-p/am-0137.htm), and the 6" version of the VEXPro wheels. We did have a problem with the VEX wheels, that is a few of rollers on the mecanum wheels did break off, after lots of usage. Fortunately the rollers can be replaced for $15 for 7.
I do feel that the AM wheels were a little smoother as well. The bolts sticking out of the normal AM wheels however tend to get caught on things, but they can easily be cut off.