bipolar unipolar steppers?

I am looking into purchasing some steppers for a xyz router table. I
have been trying to determine what kind of steppers to purchase. From
the info I have been looking at, I gather that unipolar drives are
cheaper (cost wise) and have easier to build and simpler driver
circuits then bipolar steppers.

But with bipolar, I understand, are more powerful and efficient than
unipolar steppers. I also understand that a unipolar drive can be
hooked up as biploar by not hooking up the center tap of the coils.

Here is my question. If a 100in/oz unipolar stepper is wired as a
bipolar and by using a chopper type driver would the holding torque
effectivley be doubled?

thanks