Personally, I use lake country. There was a recent poll un the machine polishing forum on pads, so far I think its up to 30 votes. Lake country is in the lead, followed by edge.
Flat Lake country pads for the PC come in Yellow and Orange (cutting) white (polishing, there is a green one aswell, depending on the line of pads) and Black and Blue ( finishing, and final finishing)
Edge pads are similar, but are dual sided, and use a quick change adaptor so you get twice the pad, and perfect centering every time.
I prefer the velcro backing plate over the quick change adaptor, but that is just me. You will produce equal results when used correctly with either pad. If your going to be using these on just your own few vehicles, two sets of pads would be adequate. Its always nice to have extras in case you drop one. However, with the edge system, you already have two sets of pads, becasue they are dual sided . . . . just food for thought
I would also suggest picking up a plastic, foam pad cleaning brush. I use that with simple green (gotta make sure you rinse the product, and simple green out very well) and the pads whic I currently have over 20 uses on look brand new.
even though those swirils are light on your bmw - your clear coat is harder than a rock . . . so it might be a good idea to have a cutting pad handy in case the polishing pad wont remove them . . .
good luck
