Well if you're swirls/scratches are that bad then a PC might not save you. The PC is designed for decent/good finishes (medium swirling, light scratching.) It makes good paint better. If the paint is shot to crap be ready to use the PC for a good time polishing. The PC doesn't generate enough heat to break down polishes quickly, but it takes a good amount of time (varies between polishes.) Its faster than by hand but not as quick as a rotary.
The PC is a great light weight machine for light polishing and UPC. It would do this job 100% over the 10" orbital. the PC is along the lines of an orbital, the pad oscillates in a random/figure 8 pattern.
Just don't expect a PC to bring bad a really really nasty neglected finish. With the right technique and polish you can make good paint great, but paint thats nearing a re-paint, try a rotary......