polyethylene wheels vs. rubber?

[chknifemaker]

Which material rubber or polyurethane(like whats made by sunray) is better for normal three wheel grinders?
Is that any serious draw backs to either?
Thanks

 

[chknifemaker]

doesn't the TW-90 grinder use them?

 

[Jason Fry]

I've been using the poly wheels from USA knifemaker on my NWG for about 2 1/2 years now. No issues.