I am a newbie as well and bought a UDM from Danase last week. Last weekend I polished swirls out of my Civic and I was overall very happy with the machine. First, it seemed to be very effective at removing swirls, even deeper ones. On my car it removed 95 - 100% of them. Deeper scratches (not swirls) required more passes but I was able to cut all the swirls in one pass with a 5" Yellow LC pad and Four Star MCC.
I have not used the PC so I can not compare but I can say the machine seemed smooth to me and the vibrations were not too bothersome. At the end of the day my hands did not go numb as some others mentioned.
As far as power, it has a TON of it. I found it very difficult to bog down which means you can put lots of pressure for quick defect removal. The machine also seemed well built overall with the exception of the On/Off switch which has been a known issue for some time and DavidB will be shipping a fix for it soon. In my opinion the chord of the UDM is not at all too short.
Overall I am very happy with the purchase and performance of of the UDM.
I highly recommend you purchase from Danase and use the 10% off 'autopia' discount code.
-Frank