I would suspect that if the RPM's are the same as a Dremel or Black and Decker... then the cutting quality will also be the same. RPM's are RPM's are RPM's. The difference will be the lag you encounter... and how well the bearings hold up to that lag. Your rotary tool may be prone to burning up quicker than say a Dremel Brand. I'm just speculating though.
Also, those burrs you have... are also pretty indicative of forcing your dremel... going to fast. Overall, I'd say slow down. I know you don't have much time... but it takes LESS time to do it right, then to do it TWICE. ;)
Here's a video... sorry for the poor quality, I did it pretty quickly so I could show you something.
Basicly, the point here is to file lightly and evenly. Make sure your file has as much contact with the sinktube as possible... so what you do to one side, will also even out the other side. This is another trick I learned from QUI-GON JINN. I hope this helps.
Caden, I'll do a sanding video later (maybe this weekend)
Frodo, I haven't forgotten about you either. ;)
EDIT: Number one way to "anger" the wife... file a sinktube on the marble-topped dining room table. If anyone needs me, I'll be asleep ... on the couch. lol (just kidding... she held the camera)