After quite a bit of research I'm leaning toward the Dremel 4300. I've decided against an air pencil--too loud and not enough compressor to run one. Looked at Proxxon, and that seems to be quiet and precise with a 0.001" TIR spec (the only TIR spec I've found), but half the current of the Dremel.
Will look for a Dumore and try to find more info on the Dotco (I found a used one for $175), as it's hard to imagine my 4.2CFM compressor able to keep up.
If cost was no object I'd spring for a Foredom brushless micromotor. At $1k, however, I think I'll go for a Dremel since I only use it a few times per month.