I have both a Porter Cable 6" Random Orbital (10-years old) and a Rigid 6" Random Orbital (2-months old). In my opinion, the PC does a much better job at sanding. It has a bigger 'throw' of how much it oscillates and a stronger motor. I have replaced the sanding pad a couple times - the foam pads seem to disintegrate in the humid Florida climate every 4-5 years or so. Subjectively, I find the PC a bit lighter and I prefer holding the barrel-motor grip vs the raised handle of the Rigid (I also prefer my ancient Bosch jigsaw for the same reason). I also prefer the adhesive style to Velcro because the sanding disks are so much cheapter - can really chew through a lot of disks. I buy them in 100-disk rolls for about $20-$25. 100 hook/loop disks would be 3x-4x the price.
The Rigid does have some advantages. Definitely has a decent dust collection system. The pad has a shroud around it that can be connected to a shop vac. This shroud probably limits the 'throw' of the oscillation which makes it a lack-luster sander. Also, the dust collection probably needs to have a hook/loop disc because the holes for dust collection go through the pad and sanding disk. Also, the Rigid carries a lifetime service warranty (need to register it); and is more easily available via Home Depot. I think I paid around $100 for it. Porter Cable is around $150.
Bottom line - if you need/want dust collection, the Porter Cable is not a good choice. If you don't need it, the Porter Cable removes a LOT more material using same grit sandpaper.
Hope this helps.
Peter
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