Steve, I've had both the Rotary and DA machines.
Rotary machines can offer a quicker correction and superb results but when not used correctly then there is a world of pain...buffer trails, burn through etc etc.
Swapped this for a DA to teach the deliquent son about it and have to say they are so much easier to use. Correction is almost at the same level.
The one i got is a Kestral DAS-6. New they are very reasonable (Clean your car do them for 79.99 with a carry bag).
If you get a set then you'll be looking at about £130 for polisher, pads and polish which is a good deal.
Best advice is to test small areas - maybe 18inchs square on your bonnet. Follow the guides about passes and speeds, use the lightest combos first and you'll be well away.
If you buy the kit and want me to give you a quick demo then I'm free most weekends though you'd need to come to me - Uxbridge.