Depends on the developer.
Itagaki, Yu Suzuki, Hideo Kojima... etc
Ilhere pretty much said both consoles are a wash. I don't know how hard that is to understand.
First party devs are the ones forced to speak PR bullshit. Unless they have freedom.
The problem is that no one is in the position to make certain judgements even before these things actually exist in their final form. Developers still don't have the hardware we're talking about in their hands and we have people who might have heard something third hand who pretend they know the final word? How specific optimizations will work in real world situations?
It is possible to comment on raw specs, x > y, certain things are objective, but it will take developers a lot of experimenting to understand how they can make certain features shine, in which kind of games, in which graphical situations.
The products have a lot in common (just the fact they're supposedly using the same CPU is huge), they're both targeted to release in the same time period and at similar prices, so logic is enough to tell us that there won't be meaningful differences and it will be an other 360/PS3 situation. That is something I believed in much earlier than specs started to leak, it's just logic and commong sense.
Then depeding on the architectural choices made we'll see different strength points. Even PS2 which overall was inferior to the Xbox was better than it at managing particles effects, transparencies and getting 60fps on screen, the Dreamcast while clearly inferior to the PS2 had an image and texture quality that PS2 managed to match and surpass just because after many years developers learned a lot of tricks in developing for the system.
So most of it depends on having talented developers working with these systems, taking advantage of the peculiarities and developing tricks to walk around the weaknesses.