Ethernet is definitely the way to go.

I currently have Mach 3 and Mach 4 with ESS on Windows 7. There would be no issues running Windows 10. I hate to say this, but with the Mach Standard Mill screen set I much prefer Mach 3 over Mach 4, even with Mach 3 being goofy from time to time. Mach 4 feels very incomplete to me and I have no interest in learning Lua to complete it on my own time, especially after paying $200 for a license. That said, the ESS is rock solid and my PC and machine tend to run extremely well. I have said this in other threads, but I often run Fusion360 and adjust CAD/CAM while that same PC actively controls my mill. This has never caused an issue.

I will be purchasing a UC300ETH controller in one of the variants to run my machine in the near future. I have a very complex project coming up, one with expensive materials, and I'm hoping that UCCNC will be an improvement over Mach 3. If it isn't I will still have it to fall back on. With Acorn or LinuxCNC that is not as feasible. That said, if I had to choose between Linux CNC and Acorn i'd probably go Acorn simply because it preserves my ability to have CAD/CAM on my control PC and avoids needing a second PC in my shop space. One counter point in the Acorn verus Linux debate is that Linux is a far superior system to Windows NT (which all Windows systems operate on). So if you have the option to have a truly dedicated controller PC, then Linux likely has the reliability factor covered, at least from an OS standpoint. It is a shame that nobody is offering a Mac OSX (unix based) controller. My Macs have up times in the hundreds of days, much like you would see in Linux based systems, but Mac computers being hardware and software that are mated (similar to UCCNC, Acorn, Pathpilot) they tend to have way less issues than Windows based PC's and Linux based homebuilt PC's (driver issues).