This is probably more device dependant and/or the way manufactures skin Android. Also some carrier bloat can cause hiccups.
For me JB on the GS3 is just as smooth as iOS. I have more app crashes on iOS. On another device, I would could probably experience the opposite. It really depends. I truly wonder how iOS would fair out if avalible on many non Apple devices?
The S3 is a very smooth device, but the Nexus 7 isn't. There's something wrong if stock Android is less smooth than one with a manufacturer skin on top.
It shouldn't be too much to expect a consistent, decent user experience among high end devices.