Using my valuation system the difference between MCab and the 12th best 3B is 7.17 points. The difference between Vlad and the 36th best OF is 5.8 points. That system puts a player at 2B, SS if they can play those positions and then OF next so a guy like Huff is listed as OF.
3B is very deep with mediocrity, in a 12 team, 3 OF league I'd say OF is deeper than 3B. When you get into deeper leagues 3B becomes deeper though.