I know the ABS system adds complexity, but I don't know how reliable it is, or whether its failure could cause problems, other than the obvious: no anti-lock protection.
Although you'll find some, ahhh... experienced riders... who reject the very idea of ABS on their motorcycle out of principle, I think there would be very few who would argue that having ABS doesn't add a level of safety in at least some riding conditions. But can't you disable the ABS whenever you wish? Some bikes have a switch; I think I recall reading somewhere that to disable the Himi's ABS you have to pull a fuse, which is a hassle on that bike? If it's a dedicated fuse, I would think that it would be pretty easy to add your own switch, so you can easily turn it off if you unexpectedly wander off your dirt road and into the ISDT.
Would the non-ABS bike be very much cheaper? If not, and if it can be disabled it at will, I'd probably go for it...