Harangody vs. Erden will come down to who picks up the NBA game the quickest. I wouldn't be surprised if they both went to the D-League this year at times, though perhaps not at the same time.
My money's on Gody. If he can hit 3s, he offers a dimension that none of our other big men can. Doc has also shown more willingness to play undersized bigs who can contribute right away (Gomes, Powe, Baby) than raw 7-footers (basically just POB). Besides, we really go 4 deep in centers (JO, Shaq, Baby, Erden), even without Perk, as Baby has ample experience manning the 5 for us. And Erden is probably behind Baby as an emergency 5.
Until he gets some NBA seasoning, Erden is likely to be a poor man's Mikki Moore (light feet, good size, but bad habits, weak frame).