I'm not discounting eSRAM, it has a role. But remember it's only 32MB, not a whole lot.
I'm just trying to compare this situation to last gen. Microsoft and Sony had roughly comparable RAM bandwidth, but 360's extra bandwidth with eDRAM allowed for better alpha effects and is one of the reasons why certain games ran a lot better (not just a function of the more smartly designed GPU with Xenos).
This time it's different, if the rumors are to believed. The bandwidth the PS4 is rumored to be going with is close to the amount that the 360 had for eDRAM (192 vs 256), but instead of only 10MB, Sony has 4 Gigs to work with.
All next-gen graphics cards work with GDDR5 RAM (2GBs normally). It's used for a reason.
It's why I think Microsoft's non-standard approach (again, if rumor's are to be believed) has more to do with their overall strategy and goals rather than them focusing solely on graphical considerations.
Microsoft wanted unified memory, they wanted a LOT of it for their OS goals along with high performance gaming. GDDR5 is expensive, and having 4 GB of it is cost prohibitive.
Speculating here, but Microsoft probably immediately ruled out the option of GDDR5 because 2GB was never going to be enough, so they went with DDR3 and originally had 4 GB. Devs complained that they wanted more. Since most of the overall design was established, it's too late in the development process to do anything but really add more DDR3 ram instead of adding some GDDR5. Now they have 8 GB. Devs appear to be happy because Microsoft added more.
Sony, on the other hand, wasn't as focused on OS features, so they probably went in with the idea that 2 GB of GDDR5 would be sufficient for their bandwidth/memory needs (similar to the PC world). But when Microsoft added more RAM, the disparity between 2 GB and 8 GB became too large, and devs fired back with complaints. Thankfully, Sony listened (or appeared to).
And now we are stuck with two different memory systems for each console due to a philosophic difference in goals and design from the onset of the project's scope.
It's why I don't really believe aegies' claim that devs universally picked 8GBs of DDR3 because that's what Microsoft has gone with. Sony could have done the same, but they didn't. Reality probably is that devs are happy that Microsoft increased their RAM after having earlier dev kits with less RAM, but it's not as though they're giving any indication as to what they'd prefer when it comes to extremely fast, but lower quantity, RAM versus slower RAM/higher quantity. They're simply happy they now have more RAM to work with.
We haven't really heard anything yet from devs regarding Sony's increase in RAM and the implications it has vs. Durango, and even aegies admits that the devs he's spoken to aren't fully aware of what's going on with Sony's system. So he's comparing dev's comments of one system where there's more complete data with another system that's been largely in the dark in comparison.