iSV57T-180 VS IHSV60-30-40-48 Servo Comparison

Hello everyone,
in the last 4 years i've been working on a cnc router on my own, i've changed many things since the beginning, the project is already on it's way and i need only the last few components such as the spindle and the motors. I've looked into cheap servo motors and found the popular ISV57 and settled on it at first. Today looking around on the internet i've discovered it's "bigger brother" the IHSV60, the first thing that jumped to me where the flange difference (Nema 23 for the ISV57 and Nema 24 for the IHSV60) and their power ratings(ISV57: 180W IHSV60: 400W!). Apart from these differences there are some other like the shaft difference, but that's not the problem i've encountered.

I'm split between those two servos, i'd like having more power as my router is quite heavy but i don't really know if it's worth the roughly 500€ more.

Have anyone had any experience with one or both of these servos, and if so what would you recommend?

Thanks in advace to everyone that has any opinion

Not sure if you want to hear this but I would suggest you skip those small servos and go for their closed-loop stepper motors instead. The small servos can be a pain to tune and the software isn't all that great either.

I'm looking for servos because of their "constant" torque even at high RPMs as i plan to run this machine at high feedrates

may I ask you, to what feed rates you got it to?
I've got some IHSV60-30-40-48 controlled by a MESA 7i76e and got stuck at very low rates.
Servo Thread is 1'000'000 ns, 5000 steps/rev, ball screw pitch is 5 mm/rev

desired resolution is 0.001 mm and 100 mm/sec feed rate. possible? or anything close to that? need to swap hardware?

100 mm/s with a 5mm/turn ballscrew is only 1200 RPM.
This is tough for a low end step motor system but should
be easy for a servo motor.

What is limiting the speed?

On my machine I've set the servos to 4000 steps/rev and i run then at a max of 12m/min.
The main limiting factor is that even though the servos datasheet states that it can have a step length/dir setup/dir hold/step space of 2500ns they start to struggle a lot, arriving at roughly 15m/min but with positioning problems, while at low speeds the servos completely missed steps. This with untuned servos at least.

I'm currently using this step timings limiting the machine to a little more than 12.5 m/min:
DIRSETUP   = 3000
DIRHOLD    = 3000
STEPLEN    = 3000
STEPSPACE  = 3000
With a 5mm pitch screw and the servos set to 4000 step/rev @ 48VDC.
Quick note on acceleration, I'm using 1000mm/min² at the moment, and i haven't found any problem even though after tuning the servos i could bump it up a fear bit and try to increase the speed decreasing the step timing. For tuning the servos I've seen this videos:
Basic tuning(more than enough in my opinion):
Advanced tuning(if you want to spend a lot of time but get every bit of performance out of the servos):