My opinion of the Big12 recently has been a high powered offense with little to no defense.. but that's from someone who didn't watch many games.. just caught the scores. The Big10 is more of a defense first conference.. hold the other guys to under 3 TDs and win sort of thing.
Here is a primer for you on the Big Ten schools for those of you who haven't seen much Big10 football:
Indiana - Don't expect much year in and year out, sometimes they sneak in a decent athlete that can cause concern, but generally the doormat of the conference. Usually rely on a passing game which doesn't work well in the conference.
Minnesota - A little better than Indiana because they usually have a decent running game, but generally no passing game to even things out.
Purdue - They are a little tricky because they have some up years. Generally they will be sub .500 in the conference.. but they do pull off the upset occasionally.
Northwestern - Generally not going to win a lot of conference games, but they always play tougher than you expect them to. Experimented with the stupid spread which caught a few teams off guard for a bit, but never works long term in the Big10.
Michigan - Expect them to take a year or two to get back.. but now that they finally got rid of Rich-Rod, expect them to regain elite status at some point. Usually a good combination of power and speed, but their recent experiment was a huge failure and will take some time to recover from.
Penn State - Down a bit recently, but don't ever count them out. JoPa knows how to recruit and they always have the ability to beat anyone.
Illinois - One word for them.. sneaky. They usually have a mobile quarterback and that always causes issue. They can jump up and bite you when you aren't paying attention.
Iowa - The consummate under achiever. For some reason they just can't ever live up to expectations. But they are always a tough game.
Michigan State - The mid-season collapse team. Better in recent years, but always seem to start like world beaters then perform patented Sparty Choke at some point in the season and self destruct.
Wisconsin - Expect to come out of this game beat up. Probably the most physical team in the league... and least classy fans IMHO.
Ohio State - Don't expect any wins here

All kidding aside, we'll see how this Tressel thing works out.. but I think you probably know what to expect from OSU. Mobile Quarterback (in recent years and near future). Decent, but not overpowering backs, and just enough team speed to make most teams underestimate. Always a top ranked defense.