Lot of weirdness here. OSU had 14 WRs earn some sort of postseason all-conference honor this decade. Easily the most of any position group from any team. So to find a natural cutoff, six of them received honors multiple times.
Of those 14 though, only 3 ever got onto the 1st or 2nd all conference teams, the other 11, never more than HM. And Curtis Samuel was the only one to ever earn consensus 1st team. Corey Brown was 2nd team, Parris Campbell was a 1st/2nd split.
Looking at the stats, I'm leaning either Devin Smith or K.J. Hill, who have very different profiles.
Smith is 5th in school history in receiving yards, and 2nd in receiving TDs, despite being 15th in receptions, thanks to a 20.7 ypc career average. That's third in school history, and the two above him had fewer receptions.
Then K.J. Hill set the school record in receptions with 201. Considering Michael Jenkins (157) was the last Buckeye to finish with over 150, that record might be safe for a minute. But he averaged just 11.6 ypc, which resulted in him finishing with nearly 200 fewer career receiving yards than Smith, and 10 fewer touchdowns, despite 80 more receptions. In fact Hill's 11.6 is the lowest of the 58 leading receivers in school history. You have to go all the way down to #59, Ray Small, and his 659 yards on 69 receptions (10.8) to find one lower.
That said, I think on a play to play basis, Hill created so many more issues.