I'm assuming you didn't mean it necessarily this way, but, my sense is indeed that Barrett is running a larger volume of plays given the differences between Tressel-ball and Herman/Meyer. Reality is that Barret's pass efficency rating is about 50 pts higher for JT. Now, having said all that, Troy's "8 games" that year were probably a little more challenging... so... things may even out. They are similar rushers to this point both around 4 ypc... though I'd bet JT has taken more sacks, so obviously there are 2 ways to look at that.
At any rate, and I say this in the best way possilble... they seem to me to be very similar players, and whatever the differences may be, JT seems the more polished QB in his first season, but its not how you start its how you finished.
Also, I think, but systemwise (now) and recent talent wise... we're much more spoiled now than we were in 2004. Barrett is following Braxton Miller and Terelle Pryor, and essentially (for that matter) Troy Smith with a blip or two aside.
Before Troy was the starter, or at least before 2006, we were having serious... legitimate conversations about whether Craig Krenzel was the greatest Ohio State QB ever... and if he wasn't we were jumping in the way back machine to find a comparison (apologies to Joe Germaine for either overlooking him or calling him old, one of the two.)