Well, really the best thing to do is go to your local Tool Store and try them out
Sounds dumb, but seriously, it's the best way
You could be using this sander for hours at a time, make sure it's got good weight and balance for you
If they won't let you actually use them, at least hold them in your hand
Upside down, against the wall....
(you can make the buzzing noises with your mouth...lol)
If you don't like the feel of it, it doesn't matter how may people tell you it's good, you won't want to use it, you'll fatigue early, etc....