pricing early on, architecture of the system, marketing
I doubt Sony will come out with a pricing strategy that beats Xbox....they will be "market priced". Architecture? They didn't show anything or really give out any nuts and bolts on how it is built...Xbox will have the same. Marketing is definitely the weakest point of Sony PS, so any improvement will be big.
The thing both companies are going to have to show in the new platforms are what sets them apart from pc/smartphone/pad gaming...and how they can incorporate those platforms with their new console. I'd still be willing to bet that both consoles will be similar in the overall scheme of things and the nuances that they have will seperate themselves when a person goes to make a purchase.
I had PS all the way up to 2...got an Xbox when the 360 came out because of the online play and the fact that I had more friends playing it. If all things being equal, and I don't see anything that truly seperates one from the other I will probably just stick with Xbox because it is what I know and am comfortable with.