I don't know anything about the Joyetech board, is the idea to have a cheaper alternative?
Cheaper by far, at least on Joyetech's side. Look at how cheap you can get a VTC Mini, under $30 some places. Wholesale prices on a DNA200 board
alone are at least (if not more) than twice that.
So, methinks the board in the RX200 won't be that much more expensive than the one in the VTC Mini, and more than likely the same board with the firmware tweaked to take advantage of the 11.1 volts those 3 batteries can put out.
The other reason you might consider this over the DNA200 version is simplicity, since everything can be done on the mod, no need for a PC.
And finally, I think this is meant to compete in the moderate-priced (around $100 or less) high-wattage TC market (IPV, Sigelei, Smok, Snow Wolf, etc), since Joyetech currently has nothing in that fairly popular segment. The non-TC iStick 100w doesn't count.