Renteria: .267/.318/.388; EQA: .243, WARP: .7
Bellhorn: .227/.339/.355; EQA: .250, WARP: 2.4
Bellhorn has a pretty big WARP edge, but the EQA and OPS are negligible.
Let's just put it this way: Our middle infield blows, especially when you compare it to Baltimore's. Hell, even Julio Lugo and Jorge Cantu are superior middle-infielders down there in Tampa.
What separated Bellhorn from the pack last year and made him acceptable (hell, it made him pretty damn good) was the power. He hit 37 doubles, 3 triples and 17 homers to go along with the 88 walks and 177 K's (yuck).
Strikeouts do not mean a player sucks. What it does mean is that they can be extremely unpredictable from year to year if they haven't established themselves on a long-term basis (Thome, Glaus, Dunn, etc.). Bellhorn's inability to make consistent contact is what makes him unpredictable and unreliable from year to year and even game to game. It's hard to predict what he's going to do next because he can frequently be overmatched.
I think it's pretty clear with Pedroia hitting .325/.406/.498 for Portland while walking more than he K's that he will be next season's 2B for the league minimum. He already presents a clear and ready upgrade to both the offense and defense. Plus, everyone's going to love him because he rarely K's, for what it's worth.