Score! Now, which axes should get which motors?

Well, I just did what I've been telling myself that I have to stop
doing....spend more money on this recent CNC infatuation.

I just scored (2) Triple Stack Slo-Syn Nema 34 550 oz-in steppers for
$60. So now I have (3) double stack Slo-syn motors (370 oz-in) and
the (2) 550 oz.in and multiple size 23s and 17s.

When my Shoptask arrives, I'd like to CNC both the Shoptask and my
Mill/Drill. At this point I wasn't planning to change either to
ballscrew because I'd really like to maintain the manual control of
the machines, thus I know the Z axis of the Mill/Drill could easily
be controlled by any of my Nema 23 steppers. That leaves the 5 Nema
34 motors to drive the other 5 axes of the two machines.

What is typically the preference for which axes get the higher torque
motors? My understanding is that its usually the Z-axis, but because
of the quill feed configuration of the mill/drill, it won't require a
high torque motor. Is the shoptask similar if I don't convert it to
ballscrew? If I put one of the triple stacks on the Z of the
Shoptask, then I'll have to mix up one of the machines X-Y. Would
the X feed on the Shoptask be the best choice for the larger motor
because its also the lathe (Z) direction?

Thanks!
-Chris