Speaking strictly from these spec leaks (no dev kits for me thus far with nextgen) it certainly does seem like Sony went with the right approach. 4GB is sufficiently into the "way more than before" range that you'd want to go for max speed and try to keep the CPU and GPU fed. Microsoft's specs smell strongly of having some other compute requirements under the hood, whether that's Kinect or magic surprise b.
Reminds me vaguely of the N64/PS1 generation, though this feels a bit like the opposite. Nintendo had elite-tier bandwidth and easily the best CPU, but latency was just embarassingly bad. We ended up spending most of the dev time trying to figure out how to keep the CPU fed. The PS1, on the other hand, probably could have used a bit more RAM to cache CD data but latency and the rest of the CPU spec were pretty good at dealing with what it could deliver.
(Well, that and there was no 4kb texture cache limitation!)
