I've recently gone from a 20" geared suspended inbred to an XL (21 1/2") geared rigid Swift.
First up the Swift fits a hellofa lot better. I'm 6'4", far more comfortable than my old HT and that's with the flat (narrow) bar that Sam put on it. The slight lay-back seat post / stem combo just right. Nothing flash but it works fine. No back ache in rides up to and including 4 hours, not been out for longer, yet.
Not convinced by steamroller-ing over stuff but on climbs there is more traction and I'm in the granny ring less, I'm no climber so it's noticeable. Also in the big ring a lot more than I was on the inbred, no idea why.
Kinda missing front suss but only on the rockier faster stuff here that heads down the hill, on everything else it's faster. That's probably as much to do with the fit as the wheel size.
And the paint job on the Swift was excellent, until I'd fallen off a few times anyway. Finishing on the frame is also excellent.