Considering the cost of these machines, I'd spend the extra for the 16" regardless of any deals Best Buy may have on the 15.4". The improvements of the 16" are totally worth it.
THIS, and the 16 inch MBP has better cooling and speakers. The speakers are insanely loud and rich in sound compared to the 15 inch which I just got refunded from Apple.
Everything about the 16" Macbook Pro is better. Prior poster has it exactly right. If you are getting the larger Macbook Pro, there is only one choice: the newly-released 16". A tremendous machine for the money.