I'm currently considering making a stationary gantry design. Since the weight of the gantry pluss the z and y cart comes inn at 80kg (mostly in steel).
The cons will be;
-Longer machine
-Longer rails
-Potensial for sag in the bed

Pros
-Less weight to move for the steppers
-Simpler design
-Less twist on the z axis, the largest factor for displacement

The reason i'm posting this is because it probably a lot more pros and cons than I can come up with, that I hope someone here will add.