Bay and by a wide margin. Bay has just started to find his groove (he's 3-3 , with an RBI as of this post). Provided he stays somewhat healthy, Bay will have weeks where he carries your offense all by himself. His production for my team last summer kept my hopes up while the rest of my team underperformed.
Rowand is not bad, but I group him in with the mid-range outfield crop, Floyd, J. Jones, Cameron, Sanders - all solid, 3-4 category players. Bay can light it up.