@BigJ Well from the sounds of it, he's not talking about gameplay related issues, he's talking about grand scale, millions of things happening, etc etc. In terms of actual processor power, the ps3 smears the hell out of the 360, and considering Kojima's team isn't what I'd call "general purpose" developers, this is a big deal :P I honestly don't think this game could run on the 360 xD He's talking about maxing out the potential of the Cell processor, and in terms of maxing, the cell has a massive edge over the 3 core setup.
No, in terms of processor power the PS3 has significantly less than the 360. The cores to the processors are similar, and even clocked similarly, but the 360 has 3 cores. The PS3 has 7 active SPEs, but those are useful for floating point calculations. Not general purpose computing. General purpose computing is what you most often need for gaming, although games are often floating point intensive, the Cell simply has an imbanace of general purpose power to floating point power.
There are things you cannot do well with the SPEs, plain and simple. This is a fact. It's not disputable.
Don't get me wrong -- if you can shoehorn your algorithms to work primarily with SPEs you'll have quite a bit to work with, but there are things you cannot do well with them and things you need to do regularly with game engines. The extra cores that the 360 offers are *extremely* valuable for game engine development, because you can be rendering one frame with one core, while doing the preparation for rendering the others (physics, animation, AI, sound, etc) which means you can easily cut frame rendering time in half (or better) from a CPU perspective.
The bad news is that if you are going to port an engine written this way to the PS3, you'd get much less from the parallelism and it's reasonably likely your framerate would directly suffer.