Ok, let's do this.
Ignore everything written in these speculations threads since 10 months
Now check a video of the japanese garden demo on Wii U from E3 2011, with AT THE VERY LEAST, a Xbox360+ content on the main screen + a 480p content on the padlet.
You know as a FACT that this demo was quickly built, run on firsts iterations of the dev kit (we are 4 dev kits after at the moment), on firsts SDK, etc etc etc.
Check a video of Ghost Recon Online with the UAV drone. You have at the very least, a current gen HD game + a different content on the padlet. Again, it was one year ago, on firsts dev kits, etc etc etc.
So you have at the very least:
A xbox360 on the main screen
A 480p xbox360 on the second screen. Let's say 480p + calculating a second view/scene/content from the same hardware is demanding, so it's roughly 0,5x xbox360
1 xbox 360 + 0,5x Xbox 360 = 1,5x xbox360
This was the situation one year ago, with all the elements derived from the very important context that i've described i don't know how many time. Add to that, at worst case scenarioS, just tweaking here and there, small boosts, optimizations, advancements in titles development, graphical polishing for these softs, devs being more and more accustomed to the asymmetrical setting (again, small improvement here), etc etc, all that since one year, you have, let's say roughly 0,5x xbox360 (through slightly better framerate, better/greater AA/texture filtering, and some things that the current gen GPU's can't handle).
So 1 xbox 360 + 0,5x Xbox 360 + 0,5x Xbox 360 = 2x Xbox 360, at the very least, considering the two screens. The Wii U isn't "on par" technologically, period, and this demonstration has always considered the worst that could have happened.