I think it's all about personal preference... I've used just about every ROM that's available for the Shift and I still can't decide which one I like best.
Here's a few of my favorites
MikShifted G - Sense2.1 Beta - Sense ROM running Android 2.3.3 and Sense 2.1 and Really smooth for a beta. Only downside is, still waiting on the source code to be released so it can't be oc'ed
MIUI Speedy - haven't ran this one in a while but it's really cool ROM, totally different than any other ROM out there. More iPhone like with no app drawer and folders.
Gingerbread-Shift-Deck - this ROM is pretty new and they're still working out some kinks but it is the best aosp ROM that I have used. It's extremely quick and smooth running Android 2.3.4. Pure vanilla Android.
Doesn't really answer your question but hope that help