UE500 has the best isolation of those two. R1 has a small vent, but still isolates decently. The UE500 can be inserted moderately deep, resulting in a very good isolation level (and yes, I have used both to note this).
EDIT: sorry to trouble your decision further, but if you are willing to stretch your budget a bit, maybe consider Etymotic MC5? It has incredibly good isolation, notably better than the UE500, and consequently also much better than the R1. It sounds different, but the isolation is better, so that should be what you're going for.
http://www.amazon.com/Etymotic-Research-Isolating-In-Ear-Earphones/dp/B003S3RFJ0/ref=pd_sim_e_4
Edited by eastPride - 1/26/13 at 8:35pm