There are two schools of thought on geared benching. Louie says to push in a straight line, but a lot of guys at westside have switched over to pressing back over the face. A lot of the big benchers advocate pressing back over the face because it gives you somewhere to go if you start to stall.
It's a longer range of motion but for most people it seems they are stronger over their face (everyone I've lifted with). I've stalled out in my shirt off the chest and if I drifted back I could turn the elbows out and flare them as I let the bar drift. Pressing in a straight line is the shortest distance but I think you need more speed (which louie implements as well) b/c you're not as strong at that position, plus if you do slow down, you have nowhere to go.
I think with raw benching, its similar to shirt benching, but with raw you don't go as extreme as you would in a shirt because you don't have the shirt to support the position.
For instance you wouldn't bring the bar as low raw as you would in a shirt, wouldn't tuck as hard as in a shirt b/c you don't have to fight something that's stopping you from touching. And you wouldn't flare back as extreme of an arc b/c you don't have the shirt to provide some resistance.