Well it's closest rival would probably be the BF30 type machine, such as the Warco WM18. The X4+ has less X travel but more Y, similar table size. The spindle is significantly slower which in my opinion (unless you are only cutting steel) makes the nicer brushless motor option irrelevant because it is just too slow. At leat you can get 2500 RPM from the BF30 which still isn't enough, but is better. In effect, to maximise the use of the machine's potential, BOTH the X4+ and BF30 would benefit hugely from a spindle RPM upgrade, such as a belt drive 3ph motor and VFD.
I have no experience with the quality of the Arc prep service so I can't comment on it's value, but upgrading the ways to Turcite is certainly a nice feature. It would be up to you to decide whether these differences make this machine worth more than twice the price of the Warco WM18 or equivalents. My feelings would be that if it was destined to be a CNC conversion, you will end up ripping out or changing some of the things that make the X4+ more expensive in the first place, so I would go BF30. But I may be biased, as that's the machine I have.