I think down is better then up. As long as you have adequate up travel (4" or so) for street driving, letting your suspension droop as far as is reasonable is actually kind of like free travel. The path doesn't care why the wheel is on it, just how much weight is on that wheel for the best traction - thus, 4 tires on the ground are better then 3... how you do that? up to you. Best of all, the lower your CG the more stable your rig will be. Of course, if you're desert racing - then ignore everything I just said (well, maybe except the CG comment).