Choosing on a stepper Motor for new printer

Hi,

I'm about to build my 3rd printer, even though I'm getting quite some experience already I'd like to hear some other advices regarding stepper motor.

I currently have a customized Prusa i3 printer and a customized Wilson II printer.

I currently run both printers with 0.9° step NEMA 17 motors (4200g.cm holding torque) for X and Y axis, I did run the i8 with 1.8° step NEMA 17 motors before, beside noise improvement I didn't see significant quality improvement.

I have make numerous experiments, and I have made the following observations

Microstepping seems to have very little influence on print quality at 1/4, 1/8, 1/16 or 1/32 microsteps @ 0.9° or 1/8, 1/16, 1/32 @ 1.8° below that noise and vibration will affect the print.

the belts have a high impact on print quality, Neoprene/glass fiber belts (standard black belts) give much more vibrations than Polyurethane/steel core belts (White belts), however the later might have other troubles due to their rigidity and tension force necessary, these are the one I use on the Wilson II but I had to strongly reinforce the structure.

I have made movement tests up to 400mm/s with the Wilson II and I didn't notice losing steps (1/8 microstepping with 0.9° motors)

Now my new printer will be a different design, it'll be a 40x40x40cm 100% metal structure cube, printing platform will be moving on the Z axis and X carriage will be moving along Y axis (I considered a corexy but rejected it). Since I expect much higher rigidity than my current printers and I might want to have a heavier carriage (converting to CNC maybe), I'm thinking about using NEMA23 motors.

I have options to go with 1.8 or 0.9° motors, I can get 23HS7628 1.8°/step motors with 18.9Kg.cm holding torque , 23HS5628 1.8°/step motors with 12.6Kg.cm holding torque or 23HM1430 0.9°/step motors with 18Kg.cm holding torque. I would use TB6600 drivers at max 1/16 microstepping.

Since motor prices are quite different, I'm curious to have a second opinion. I think the 0.9° will probably not bring any quality improvement since the limitation will still be mecanical, and anyway since the motors are much stronger than nema17 I can go further in useful microstepping. I can get a sweet deal on the 12.6Kg.cm motors, and I'm hesitating with the 18.9Kg.cm ones (1.8°) which are 50% more expensive.

Or... should I just stay with cheap Nema17 motors?

Any thought?