Are there any centers left?
Orlosky looks like a good, solid option. Although a bit undersized, he's a strong run blocker. He seems to be able to control his man fairly easily. Looks decent in pass blocking. I like him. Not the most athletic-looking guy, but he looks good, solid, strong.
Toth looks more athletic, is a pretty good pass blocker and adequate run blocker. He looks confident, solid, aware.
I looked at some videos of some good DL prospects with the purpose of watching other centers to compare to Toth and Orlosky. None of the centers looked bad, so it's not really easy to see what makes one guy better than another.
It seems the big thing is that the good ones show a "dominant trait"...something you can hang your hat on.
Orlosky is strong and latches onto a guy (not holding) and moves the pile.
Toth is big, strong, confident, effective - looks like an NFL-quality lineman.
It really depends on what sort of guy you want. I like them both...would lean towards Toth only because he seems to have more "upside".