The Defense Secretary takes orders from the President. His job is to win wars. I trust Powell to do that. He's done it before.
On that basis, Franks is my pick, though I think he and
Rumsfeld had difference it appears from reading his book.
The SecDef doesn't just 'win wars'. As a matter of fact, I don't think that's his job at all. I think it's up to the JCS to win wars, coordinating strategy through the various theater commands (Centcom, Northcom, etc.).
The SecDef is the guy that is responsible for making sure that the nation has the right forces and tools to do the job we are going to be called on to do.
Rummy has begun a massive overhaul of our forces, and how they are equipped. It was long overdue. I'd want someone in there that would see that plan through.
He was all for stopping the Gulf War.