So I've been using strictly a rotary since I started this insanity and just finally got a PC... bought it because ummm... why not? So what is better to do with the PC than the rotary?
If you get a PC Guard from show car detailing, you can work a pad under doorhandles to get at the scratches. On some plastic pieces, it may be better to use a PC due to the heat generated by the rotary.
A couple of big advantages: A pc's performance is not affected by sticky paint. So now when you run across a vehicle with the issue, just use the PC. The second advantage is applying sealants.
I keep forgetting about that nifty little tool accessory. I'm going to have to remember to pick one up soon.