Most importantly, if you've never had any machine polisher type experience, I wouldn't jump into a rotary unless you have something to practice on that has no type of consequence. I have heard of people buying hoods at a junk yard just to practice a rotary on.
If you're not intending on wet sanding, or doing anything intensive, you will more than likely get by well enough with any of the DA's. Flex, and the PC are probably the most popular, but the Griot's Garage polisher offers a lifetime warranty, and is the strongest. The big difference between the Griot's and Flex is that the Flex has forced rotation, making it almost impossible to apply too much pressure to force the machine to bog down, whereas the Griot's just has a stronger motor.
Stick with the mentioned machines, and you'll have some pretty surprising results. As you get more familiar with technique, you'll be confident enough to move to a rotary for more correction capabilities as needed.
Good Luck!