I'm confused, which are better uni or bi polar ?

I read the posts today about running a 5 volt stepper at 48 volts, ok
more voltage is a faster start for more torque out of the chute.

then there was talk about re-wiring a uni to make it a bi polar.

this is a bit beyond me. I have a couple NEMA23's some bi polar some
uni polar. I pulled them from old printers but am not sure which is
better/stronger/faster.

I'm driving a drill press, 3:1 ratio using XL belt, but I also need
to drive a lead screw, direct drive. Positioning a drill press
table, so no real loads, speed is more important. is one stepper
better than another for these applications ?

and while I'm at it, I've read most of the sites explaining steppers,
but they mostly go over the basics, not how to power them to higher
voltages than the nameplate. can anybody offer any links ?

tia


Dave