which Neu 1515 has the most torque/power?

[What's_nitro?]

You should definitely invest in a rotary tool of some sort. They aren't just for R/C, you'll find lots of other handy uses for it. Plus, it will make that flat spot in about 5 seconds and without having to clamp the shaft.

My workshop (since a few others posted theirs):

14" drill press, 12" band saw, 12" scroll saw, 8" bench grinder, cordless drill, large and small rotary tools, soldering gun/iron, and pretty much every hand tool related to R/C.