I LOVE my cyclo, but if I had to choose between the two I'd consider this:
-If you are using it on your rides, and take good care of them, the PC and/or cyclo should fit the bill 99% of the time.
-If you are detailing cars that are not very well cared for, and want to 'get the job done' in a reasonable amount of time, then clearly the rotary is the answer. I have Dewalt & Metabo rotaries, and the Metabo is a dream machine. It's set up almost identical to the PC and has a unique feel wrt rotary polishers. It costs a bit more, but it's worth every penny IMO. The Dewalt is an excellent tool too, but it's much heavier and much more unforgiving vs. the Metabo. You'll need some rest after a day with the Dewalt
-Good luck.