I've never used the UDM, but the PC is pretty bad vibration-wise compared to my rotaries/Flex/Cyclos.
My rotaries aren't nearly as smooth as I think they oughta be...not sure what the problem is

I sorta think I have wobbly spindles...I thought it was a problem with my backing plates (what, all six of eight of 'em?!?) but it's not smooth with my Edge stuff either (better, but not smoooth). Eh... :nixweiss
bwalker25- with the right products (e.g., M105, 1Z Pasta Intensive) and the right pads (esp. 3.5" PFW and 4" stuff) the PC can do a lot more than many would ever imagine. Even on hard clear, I'll usually quit for fear of overthinning the clear instead of because I'm simply giving up. Note that this is *VERY* different from what I woulda said a short time ago- the product/pad combos are critical and effective/efficient stuff only recently came on the market.
Ditto for working by hand. I've removed bad fingernail scratches from behind Audi door handles by hand...used to take so long that nobody in their right mind woulda stuck with it until the job was done. Now it's not *that* terrible...in the worst cases you can wetsand with ~2K and then clear up the sanding scratches with something like the M105.
But I'm pretty amazed by how well the Flex works...I was hesistant (to say the least!) to buy yet another polisher, but I now consider it money *VERY* well-spent.