Cant really go wrong with the Porter Cable 7424, thats what I've got and for swirl removal with the right polishes its great.
Polishes I use are Menzerna Intensive Polish Po85RD3.02 and Menzerna Final Finish 106FF.
Jeffs werkstatt acrylic Jett trigger as sealant and you're made
My brother has the UDM ultimate detailing machine and that seems like it vibrates a lot more [giving the old numb hand syndrome]
That said, there not that much difference from what I've heard from mates who have different versions - i suppose its which one you can get the best price on really.
Def need 6" pads and 4" pads - you'll need a 3.5" flexible backplate for the smaller pads.
The Sonus SFX ones I use are yellow [light cutting] white [polishing] blue [glaze/wax] Though I tend to find the blue ones surplus to requirements.
Couple of befores and afters
BMW Z4 3.0Si before
After
Before
After