Once one of these three does that they will be the new mach3 as controller of choice as regards easy setting up foe beginners and semi- skilled.

I think that UCCNC has a big advantage here.

1) UCCNC was designed to "feel" very much like Mach3. They both have very similar controls, and the setup is very similar.
While the macro language is different (C#), it's very similar to Mach3. The terminology is very similar, with buttons, LED's, and DRO's.
UCCNC also has an integrated screen designer that's far superior to Mach3's, (Screen4) if you like to customize the interface.

2) Mach3's success had a lot to do with the users, pushing Art to add features and make it better and better.
While Terry and I don't often agree on things, we are both trying to get all of Mach3's capabilities into UCCNC, without any of the bugs. There have been new releases every few weeks, with both new features and minor bug fixes.

I don't have any experience with PlanetCNC, but I've heard that it works well.
I seriously considered Eding CNC, but it just seemed a little too "non standard" for me. Bert seemed to be very helpful and accommodating, though.

On the subject of hardware.
The UC300ETH is really no different than a Smoothstepper, which is hands down the most popular Mach3 motion controller. Both need similar breakout boards, and with the M44 motherboard, some breakout boards designed for the SS can be used with the UC300ETH.
The difference, though, is that I've seen years of poor plugin development from Warp9, while CNC Drive provides fully functional firmware right out of the gate. With bug fixes in days, rather than years.

I forgot, there is a 24V motherboard for the UC300 from Hungary:

https://www.cncpart.hu/uc300-5441

I need to ask some questions about it to CNC Drive.