I did lots of research when looking for a palm sander myself. Eventually, I read an in-depth review (Wood magazine I think - or maybe Fine Woodworking) which tested around 8 models. Based on the speed of material removal, vibration, quality of finish, dust removal: the best one was the Milwaukee 6021 5" Random Orbital Sander.

I bought mine from Home Depot, as the savings on the TAX and selling price, were offset by the cost of shipping.
I'm very pleased with it and have no regrets.