Yes, both the USB and ethernet UC300's need a breakout board. (or multiple breakout boards).

The ethernet UC300 is more powerful and faster than the USB version, and the cost is about the same.

Imo, UCCNC is much better than Mach3. Better trajectory planner, and mostly bug free. If you find a bug, they'll usually have it fixed in a few days.
It's missing some features that Mach3 has, but for most people, but they are features that most people don't use anyway.