As others have said, I think the difference is that Ohio State Zeke was running behind a line of some absolute freaking hogs, while Barkley had a really mediocre OL in front of him. I mean, just look at that Sugar Bowl he had against Alabama. Alabama had eight guys on that front seven that ultimately went in the first 2 rounds of the draft, and Ohio State pounded the crap out of them.
Barkley likes to bounce it, but I don't think it's as big of an issue as some are making it. Part of it's because he could - he was a freaking 99th percentile NFL athlete stuck up against college players, - and part of it is that he was The Guy for Penn State's offense, and he pretty much knew it was all up to him to make plays. It wouldn't surprise me at all if he's a much better inside runner in the NFL than people are expecting.
Anyway, Zeke and Barkley were both blue-chip studs as prospects, and it's tough to sort between them. With Barkley, what you see is what you get - an 99th% athlete who's drawn comparisons to a 230 pound Barry Sanders and Marshall Faulk. Zeke is a little different, because he wins in ways that aren't as easily quantifiable as a 4.40 40 or a 41" vertical jump. As Brett Kollmann said "he's not elite in any one area, except maybe strength". But whereas Barkley constantly tried to use his athleticism to hit home runs, Zeke's goal is to get positive yardage on every play, and he gets there through a combination of vision, power, smarts, and endurance that don't show up on a Combine drill.
Watch the end of the second Washington game, where Zeke ultimately took 33 carries. Start at 1:56.
We were holding a one-score lead and looking to burn clock to put the game away. Zeke was at ~25 touches and was starting to gas out - he had noticeably lost a step, but the defense had too. And he was STILL banging away on those guys - hitting cutbacks, dragging tacklers, and just creating positive play after positive play. There was one play in there at 2:24 where the Cowboys wanted to run a left-side stretch, but the NT jumped the play, slashed inside and put Frederick on skates. Zeke's looking at the edge (as RBs are coached to do on zone runs), but once he sees #71's big butt coming at him, he immediately cuts back into the hole the NT had left and gets 4 yards. This guy's on his 30th carry, and even when you blow up the play, he's still improvising for positive yardage. How do you stop him?
Cause of Zeke's dominant 4th quarter rushing, we were able to put that game away and get the W. That's how he wins you football games.
We'll see what Barkley's got in him - I'm seriously expecting a Kamara type impact as a rookie, and maybe a Todd Gurley kind of player long term (that's personally my comp for him). But I'm more than happy with Zeke.