I think both are winners. Most people said Jenson was stupid to go to Mclaren (I wasn't one of them as his ability as a driver was never in doubt as far as I was concerned [some of his contract choices on the other hand...]). After the pairing, who out of the two current McLaren drivers was the first to win a GP? Some people say this is down to luck, but you make your own luck in this world and nothing is handed to you on a plate. Yes, Lewis is slightly faster than Jenson and can usually get that little bit more outt of the car, but it is only a little and in this game, speed isn't everything. If it was, Lewis would have 4 WDCs by now.
I think McLaren are standing by what they see and going for the best deal they can get at the moment.