‘Wii U eDRAM usage is comparable to the eDRAM in the XBOX360, but on Wii U you have enough eDRAM to use if for 1080p rendering. In comparison, on XBOX360 you usually had to render in sub 720p resolutions or in mutliple passes.
Even if you don’t use MSAA (MultiSample Anti-Aliasing) you already need around 16Mb just for a 1080p framebuffer (with double buffering). You simply don’t have that with XBOX360 eDRAM. As far as I know Microsoft corrected that issue and put also 32MB of Fast Ram into their new console. - Manfred Linzner of Shin’en