I am really having a hard time with the Tim Beckham school of thought that says he'll be a 40+ SB guy. All reports I've read indicate he has average speed, and as he matures, it will likely translate into even less speed, although he won't be a station to station guy at any point in his career. His best tool is definitely his bat, with strong wrists nad above average bat speed. Furthermore, short season debuts are almost always not a true reflection of a players ability, as he makes the adjustment from metal to wood bats in Beckham's case, and faces professional pitching for the first time, all while we try to measure what his stats mean within a very, very small sample size.
As for who I would take, if you need help sooner rather than later, grab Gordon. He'll probably be up once he has a hot streak in AA, and with less than stellar placeholders (Getz, Nix, et al) at 2b in Chicago, he could easily handle the transfer over to the bag and provide some counting stats in 2009.
Hope this helps!