Well a rotary is like an angle grinder, and can easily go through to the metal in the wrong hands.
You also need a paint thickness gauge, circa £500.
So a dual action is the one for amatuers and enthusiasts really, is a lot safer, yet still achieves good results.
I have the new meguiars, got mine from polishedbliss, was £150 with 2 pads.
What polishes you use depends on what paint you have.
If german, can't go wrong with menzerna.
If ford meguiars is good polish and highly rated.