OFP has the best outdoor terrain and handles trees better than any other game I've seen. Its buildings are a bit blocky and really are more asthetic than anything. The tree lines is where the action is on this one. Also... sandbags and walls are also very well done. It does also have the best maps too. They are simply huge.
MOHAA does not really compare. Not even close to OFP. Its a good game, but they aren't even in the same league.
I have a tendancy to give the nod to Ghost Recon for overall squad shooter. Its good for indoors and outdoors. It doesn't have many trees, but it does cliffs, caves, tunnels and buildings quite well. And combines all of them on most maps.
Been playing alot of Raven Shield lately too. The AI is one of the smarter I've seen. It will hide and flank you and isn't nearly as predictable as most I've seen. Though, they seem to have slowed the AIs reaction time just a bit. I somewhat think that was a move for the better. They also handle magazine changes and various aspects of stealth really well. Its main downfall is it is indoor based almost entirely. Small, but complex maps. Its really good for deathmatch type rounds... and killing FDBs.
MiniD