The air/raft is a lot smaller than an ATV and its open to the environment. And it is still like 50% more expensive. If you want an environmentally sealed, 8 person off road grav winnebago, that's a lot more expensive than an ATV. A G-Carrier is like 100 times the price of the same capacity ATV. Even if you reduce the G-Carrier's armor and weapon mount to match an ATV, its vastly more expensive. Obviously, if price doesn't matter, grav vehicles all the way.