Whoever gets into the better situation will end up the better QB. I think both are tremendous. But in those early years if your o-line sucks and you have no one to throw to, it can really do damage to a rookie's confidence.
The colts seem to be in full on rebuild mode, assuming Luck goes there, he is going to have no one to throw to and their o-line- which was mediocre, lost pro bowl center Jeff Saturday. Now the redskins don't exactly have a great o-line either, but they hit free agency hard and at least got some talented receivers.
Whoever goes to the Colts has huge shoes to fill with little help doing it.