MUCH better. I have a friend who has Ascend and it's crap compared to Optimus M. It's very laggy, feels cheaply made.
Ascend has 2.1 and 256MB RAM.
Optimus M has 2.2 (more built in features like voice input) and 424MB RAM (or maybe it's considered 512MB but it only shows up as 424?) Anyway, much more RAM.
I've handled 3 Optimus M (mine, my wife, a friend's) and one Ascend. All the Optimus are more responsive, even if not rooted.
I had an Android "party" the other night to show my friends what settings to use, how to download apps, how to swype, and all that. My wife and I have two Optimus Ms. The two friends had an Ascend and an Optimus M. I handled all the phones during the course of the evening to demonstrate stuff -- and I am so glad I never even considered the Ascend.