In the 40 size category, both work well. I have both but my personal preference is with the 4 strokers. I have a YS63 on a Burrito and a Webra 50 on an Extreme Flight Edge. Comparing these two setups, the burrito responds much, much quicker to throttle changes. I am not talking about spool time, I talking airplane response time. I can punch the throttle on my Webra and hear it rev up while it gradually climbs out. I don't really hear the YS rev, the plane just jumps when I hit the throttle. I had an "accident" a while back with the Webra/Edge. I doubt it would have happened with the YS/Burrito. The Burrito would have been up and away before any contact was made.
On the other hand, you can't beat the economy of the 2 stroker, both initial puchase and fuel costs! I'm sure I'll always have both on my profiles.
Matt