More 'n' one way to skin a cat!
My Sioux angle head sander is at least 20yrs old now.
I purchased it strictly for sanding bowls, and back then I wasn't aware of the current thinking regarding "slower is better"......so, it's the faster 0-2500rpm variety.
I'll have to admit that I've had a few bowls with burn marks created by heat from sanding.....and it sure has bugged the hell out of me when I've finished sanding and the burn marks become visible only after I apply a final finish on the wood! (Cherry seems to be among the worst for these phantom burn marks!) There have been a few bowls in my distant past that have been completely re-sanded after applying the finish.....grrrrr!
I'll tell you one thing, though......I'm glad I've had the experience of learning the hard way about sanding speeds.....rather than just listening to the voice of experience and getting something slower in the first place. As a result of this, I've had to learn by seeing, and experiencing what DOESN'T work!
One thing I've learned is there is a definite time to use all of that 2500rpm I have available to me.....and there is a time to use much less rpm....and everything inbetween. If your bowl has blemishes, or torn end grain, and you decide to go to 60-80 grit for starters, that's the time to use higher speeds. I've come to appreciate the higher speeds for aggressive initial sanding......sure beats the heck out of waiting for a slower speed to do what a faster speed does much quicker! Even if you do create some burn marks with the course grits, subsequent finer grits will remove them.
Generally, the finer the grit and/or the denser the wood, the slower the speed.....but, of course, there are exceptions to every rule! The Sioux angle head sander works well at any speed because there seems to be no power loss throughout the entire usable speed range (or, at least not enough to make any difference). It doesn't take long to get the hang of putting your 3rd finger underneath the Sioux lever for adjusting to any speed you desire.
MichaelMouse makes a very important point about the use of pressure. It's an important part of the equation, and one that becomes increasingly critical with finer grits. I've also had some trouble with sanding laminated bowls that had alternating end and long grains. Here excessive pressure will cause noticeable indentations in the long grain. It does require a delicate touch for pleasing results.
Remember that the larger the bowl, the faster it's outside edge is moving.....that plays a role in your choice of speeds, too! I seldom consider sanding at lathe rpms higher than 1200, and that would be a rare case......a small diameter bowl made from wood that sands very easily. Most of my sanding is either 370 or 650rpm. I would probably go slower than that if I could.....but, I have step pulleys, not a variable speed
....odie