Another thing to think about is an Acme thread is about 30% efficient as opposed to a ball screw at around 90%. That is to say that if the pitch were equal, it would take about 3x the power to run the acme screw.
On the other hand as this is the Z axis, the acme screw will hold its position when the power is off and the ball screw head will likely drop unless you have a brake on it.!
Yes, you can get acme in zero backlash as well as ball screws so that is a wash!
Art
AKA Country Bubba (Older Than Dirt)