D. Tail -
All D/A Random Orbital machines need speed to keep the pad rotation going.
If I ever use one like with a 3" pad on badly water stained glass, I run it full speed to get as much pad rotation as possible to break down the glass compound.
The Porter Cable Sander/Polisher machine is not going to rotate all that great either, but fortunately, there have been a few good advancements in compounds and polishes, so that supposedly, one can use a machine like this and get pretty darn good results.
But it will still take longer than a good Rotary ( DeWalt, Makita, 3M), and there will be Vibration, which may or may not be a good thing to deal with long term..
Your hands and arms will have to absorb the vibration through the handles and I think that over time, it cannot be good to your body to a certain degree..
Now, if you only do this once and awhile, then it might not be as bad..
I dont know the pricing but a lot of people over a decade+ have gone to the Griot machine and had good results with the power and I guess pad rotation of it.. And they have or used to have a Lifetime warranty, and many have had to use that because they break down with hard use apparently..
There are more expensive machines in that line like the Flex 3401VRG which is more forced rotation random orbital, but still not a true Rotary, and the Rupes machines which everyone really likes around here..
Like I have said before, pad rotation is what helps break down the product with the pad and clean, level, and polish the paintwork to a great place..
The Random Orbital machines all do this, some better than others, but you need to run it full speed and make sure its still rotating.. Draw a straight line with a Sharpie on the top of the backing plate so you can observe it going around and the speed it is rotating..
So yes, an accomplished Detailer and about everyone else who wants to put in the time and effort, really pay attention, be really innovative and try new things until you find the best process for that paintwork that day, and work at this a lot can do some pretty darn good things out there if you want.. You just really have to want to... It all comes down to that...
Good luck !
Dan F