I gotta say it's mostly an on road vehicle, come on; don't the majority of Explorers (and other SUV's for that matter) go to women? They pretty much replaced mini-vans as the soccer mom vehicle of choice. Or in the case of the Hummer H2 men trying to compensate for some other shortcoming.
I mean if this was the early 90's and someone asked me "Do you think Broncos are mostly on road, off road, or a mix" I would then say mix, because they were just F-150's with seats in the bed. 100% of the people I personally know that own explorers use them as on road vehicles; myself included - this thing is too pretty to beat the bag out of on a trail or mud bog, and besides it doesn't have the ground clearance for it (stock anyways); thats what my 93 F-150 with 3/4ton suspension is for... I dunno maybe it's different elsewhere. Oh I should mention, I don't know any men (aside from myself) that own an Explorer, only women. The guys I know that own something with a worthy tow rating own Trucks; and most of those are primarily on road vehicles too. Take for instance, my Brother - 2009 F350 Diesel he uses for Work (hauling a bobcat, sanding, plowing, gen. construction etc.) awesome truck, but an on road vehicle. He has a 1977 F-350 with a 400M, 4-spd, 4wd and stump pulling gears (4:56's, straight axle front end, locker rear) for off roading, and although it red lines at about 55mph in 4th gear, it's great for bogging, or trail riding, and parts are CHEAP!