This has to be one of the toughest questions on the board today... Every time I look at it, I come up with a new "right" combination, only to have second (and third, and fourth...) thoughts.
Right now, I'm leaning toward Thomas and James in playoff leagues, and Thomas and Williams in leagues without playoffs, although obviously Thomas and McAllister would form an excellent core as well. It's unbelievably close. Yikes!
I think the crux of the whole matter is James. Once you decide whether to take a gamble on him or not, the rest of the decision becomes a bit easier. It's still awfully tough, though...
At any rate, it's a nice problem to have.