I'll be the only one who won't recommend a specific polisher. Why? Because I don't know your preferences. OK, even if you are a newb, you still have some idea about a theoretically ideal machine.
My theoretically ideal machine is smooth, has low noise/vibration, good power AND torque, a really practical RPM/OPM range, and MOST IMPORTANTLY, great ergonomics. Our hands are the same with 5 fingers and a certain anatomical limits. Yet machine manufacturers pushing out products which have speed dials at the back of the machine, and other idiotic features. How'd you like a car when its gear selector would be placed in its trunk?
A polisher needs to be guided, so the grip is extremely important. It needs to be tight, secure, to ensure proper maneuverability. The trigger has to move in a nicely weighted, smooth way and has to feature variable speed control. The speed dial has to be placed at your thumb with a horizontal (lateral) dial, because it is the most natural way anatomically to change machine speed intuitively on the fly. A vertical (longitudinal) dial can be a similarly good solution. Nice detents are important too to give some feedback about your actual speed settings. Think of them as column stalks of the machine; ideally, symmetrically placed workers - for both right- and left handed users. Until our bodies stay the same with the same anatomic properties, the machines have to adapt to us and not the other way around.
The handle is an important thing too. Basket or bail handles are the better ones as they offer more flexibility than side handles. A hand guard cap on the gear housing head is a good solution too.
The length of the machine is like the wheelbase of a car. Long WB offers high stability, better tracking, while a short WB (aka a more compact polisher) is more agile, maneuverable. Combine this with the golden mean of weight (philosophical middle between two extremes) and you’ll have a great machine. The ideal weight is around 2-2.5 kg/4.5-5.5 lbs, but more than 3 kgs or 6.6 lbs is considered heavy.
Vent hole placement is an often overlooked thing. The openings must be placed properly, otherwise you may block them with your hands unintentionally causing minute overheating which may lead to premature failure. The machine blows air through its head and gears, so it is important not to blow this air into your face. I’ve worked with a cheap rotary, which blew air right into my face; it was not so pleasant.
Practical RPM/OPM ranges are 500-2500 RPMs or up to 13000 OPMs. When you choose a DA machine, be sure that the pad throw is at least 4 mm. With a high OPM, this will give you surprising power, and excellent finishing ability. Finishing with a rotary is just as important so choose a machine which goes well below 1000 RPM. More than 2500 RPMs are very rarely used.
Good serviceabilty (brush change), and a long cord are further positive points.
And NO, the Flex is not limited to just 6� pads:
YouTube - Edge 2000 Flex Conversion!!!!!