I second what RunforestRun says. I take my forester onanything that slighty resembles a dirt road, and the Foresters are pretty capable off road, if you have any doubts, just look at some of the Australian Forester owners on Subaruforester.com. And the only other advice I can give you is that the forester is probably the has the most utility out of the three. Off road, the WRX wagon is okay, but lower ground clearance. Baja may have higher ground clearance (I'm not really sure, I thought both were 7.5 inches), but it's probably not the ground clearance that will be an issue. I haven't measured both of them, but just looking at it, If anything, that will be the part that's going to stop you. the Baja suffers the same problem as the Outback, that's the rear bumper.The forester overhangs are shorter, so that's better in rough roads. And then there are the lift kits and suspension upgrades you can do if it's still not enough
As for space, I think the forester offers more USABLE space than the WRX wagon, and maybe even the baja. It's more square shaped, so the hatch doesn't intrude as much into the interior. and if you need to sleep in it, you won't have to squeeze through that switchback like in the baja. Plus, since you live in L.A, you probably want to keep your stuff locked up at all times, something you can't do as well in the baja with the open bed. And if you want to add a roof rack, the forester will hold a larger roof rack than the baja.
And finally, you should get the forester XT all of us Socal people can come over and get a ride in it. I call shotgun. Plus that'll be one more forester owner when we start having meets.
Oh yeah, where are you going on these rough logging roads? Anyplace local? Because I want to go.