the PC is 95% idiot proof its practically impossible to do damage to the paint even if you dont know what your doing....
the Rotary is alot easier to mess a finish up...people fear it a 5000 dollar paint job that can be polished a bit slower by PC but virtually risk free....rather saving some time with a rotary but increased risk...
all in all i say if your comfortable with a rotary by all means use it it cant hurt to buy one to have in the arsenal id like to get one but i need to master the PC before i upgrade to a rotary