I've been told variable speed is favorable.
Don Favell had a Chaublin 102 lathe that I believe had a 3 phase motor that he had wired to some adapter circuitry to let it run on 115 volts giving him excellent speed control.
Regarding the Precision Matthews Vertical Mills.... they look great but I don't know much about this equipment.
they are Chinese, with a few models being made in Tiawan. American machine tools are getting much harder to find in good condition without being worn out already, & the Chinese are making old machines somewhat obsolete it would seem. I love my South Bend lathe & Taig mill, but I've been outgrowing them for a while now. I'm still looking at Facebook marketplace daily for some lovely old American iron.