I had good luck with Isospeed Professional (both Classic and New one) as crosses. They are slippery, resilient and feel soft and stretchy. Most importantly (for me), they stay slippery for a very long time.
There are plenty other strings that are soft and nice, but they either have a textured surface (ie. not slippery from the get go), or their surface is so thin that it wears out in an hour or so.
I was not impressed with RIP Feel. Sippery-sure, but no resilience or snap-back.
Forgot to mention: for some reason, I also had good luck with Wilson Syn Gut Exteme. This is definitely a hard string. But maybe because it is so hard, it notches very little, and the mains slide on it quite well. Never expected it behave so well, as it is hard and cheap, but it works very well as a cross.
Last edited by tball; 11-19-2012 at 05:54 PM.