This is my experience;
after 12+ years, a lot/most full time, I got a CSMIO-IP-S about 1.5 years ago.
I also went to step/dir AC servos about 2015.
Both real industrial 220V and 60V cheap 400W ones, I import in packs of 10.
There is just no comparison.
The servos accelerate to 3000 rpm in 10-20 ms, no-load, yes 0.02 secs or less.
On a full, heavy machine, like a mill/VMC the steppers did very well ... and about 800 rpm in 0.7 secs or so.
With a 200 kg table, 200 kg load.
The smallest servos will do 0.05-0.1 secs to 3000 rpm. (I dont want that. Neither will You.).
On a very heavy Very Good, *industrial* lathe, the 220V ac servos I used and import;
will do full-peak acceleration (probably) in the same 10 ms with a 200 kg carriage, and 2 toolchangers massing 100 kg.
I will never try it, because it is a huge impact load and totally unnecessary.
5 less than-possible is still 5x better than the ("best") steppers- for the same money.
A lathe needs max acceleration at threading pullout and blind-bores pullout, where repeatability is critical and rpm is high-as higher rpm = much better finish/accuracy due to better sfm rates.
Steppers have low dynamic range.
So they are strong, or fast in rpm, but not both, and only semi-accurate relative to any modern servos.
But steppers are really cheap and really good .. where one does not need excellent dynamic range, or very fast speeds AND low speeds OR high accuracy all at once.