Better to run the alternate spindle from a variable PS than to use PWM?

I ran some tests on my 2418 DC spindle, and I found that the answer is yes. I wondering if others have tried it on the alternate spindle ( in the parts list, and, if so, whether they got the same results.

Why? Details?

Empirically, the 2418 spindle just runs smoother and quieter. Much less vibration. Go figure as to why that is, but it is.

Same voltage? A lot of the smaller stuff (including out steppers) run better on there higher voltage limits.