Looks like the new X2 BLDC motor/head/Z axis on the extended X1 base. I have had both machines in the past, and they were good for learning, for sure, but I still can't see a reason to buy one over a BF16 or BF20.
Enhanced BLDC motor without plastic gears that will break.
stiffer column due to wide leg and 4 mounting bolts
bigger work envelope due to the bigger table
Easy to access spindle mounts for a fast and cheap CNC conversion.
Apart from that, itīs pretty similar with the X2 and mods are interchangeable. I altered my X2 clone in a similar way, more motor power, bigger work envelope and a stiffened up column mount. Wouldnīt have done it if I had the enhanced Arc X2. The z-axis feed is still annoying but itīs o.k. if you tweak it.