IMO specs mean very little in terms of graphic jumps (Graphics seems to be the bench mark for console comparisons)
We are IIRC at the point of diminished returns where graphics are concerned. It takes a lot more effort for the hardware (and developers) to get a noticeable increase in graphics capabilities.
So whilst there will be a difference, it will not be the sort of leaps we saw in the previous generation or the size of the leap between the last generation and this generation.
If I was to make an analogy:
The PS3 is like a sledgehammer trying to crack a walnut
The 360 is like a regular hammer trying to crack a walnut
The Wii is like a walnut cracker trying to crack a walnut.
The end result is the same, its just how much effort you put in to getting it.