Kind of a loaded question, I know.
Based on 2005 numbers, I'd have to say Sarasota for me. Medlock, Pelland, Valdez, even Edens is starting to pitch well. Medlock should go to AA this year, and sadly, Pelland will likely join him (though he should repeat High A.) Valdez should also repeat, as he struggled in AA, but Basham made the progression quite nicely, and will probably be ticketed for AAA. Guevara and Barreto both had nice numbers in relief and both had more K's than IP.
Since we won't really know who is going where in 2006 until April, looking back I have to say Sarasota was the Reds best pitching club.