Hey NLAlston,
Note that these dedicated milling motors are still universal motors and do not have the general advantages of spindles (=asynchronous induction motors) (see also Difference Router / Spindle). A spindle, that forcibly needs a VFD, will always be much superior to any universal motor in terms of performance, efficiency and longevity.
But the dedicated milling motors strongly differ from hand trim routers like the Makita or the Dewalt in that the latter are only made for short-duration, hand-held use, and loose their warranty as soon as you mount them into a CNC, while the dedicated milling motors are made for use in a CNC and have an all-steel motor flange, also there are models with ER collets and speed control interface, which makes it easy to let their speed be controlled by the CNC controller and thus by the g-code program.
What I think makes them so interesting, is that they don’t need a VFD. They simply work out of the box, plug-and-play on a domestic sockets, no VFD, no custom wiring, and the wiring for the speed control interface over an analog control line to the CNC controller is easy too.
Yes, of course they are much more expensive than a Makita hand trim router which was already offered under $/€100. But you get something different! 