D90 hands down is the better vehicle off-road.
I salute the H1, a much more capable vehicle off-road than the H2, but as stated previously, it's too wide for most trail running,,, and downright dangerous on mountain shelf roads. I've seen the H1 take some insane off-cambers, but not significantly better than the D90. Furthermore the H1 has a poor break-over angle (though not as bad as the poorly designed H2).
The 90 may have smaller tires in stock form but gives up nothing in articulation. The 90 can take just as extreme off-cambers with a better breakover. It's solid axles make it easier to modify. It's narrower stance allows it to go places the H1 would hang up.
There's a reason why our SF units like the 90,,, it's analgous to replacing the 1911 w/ the Berreta, only to have our elite units choose to stick w/ the 1911.