I think that the dual rendering (talking about 3D output, not when the gamepad only is outputting a 2D menu or something like that) adds a dangerous factor, fluctuating performance. Let's say that both are showing a viewport of the scene. If the output of both are on a similar region, textures and 3D models will be the same and will be cached. Now, if they are showing different parts of the scene, we will have more textures and more 3D models, so performance will likely decrease. My point is that changing the vieport in one of the outputs will make performance decrease without any change on the scene and that is harder to optimize.

Anyway, the slow part is rasterization and it will be done twice unless the image is the same on both. But the situation above made me think about how it will handle cache here. Basically, if the models, textures, etc are different on both outputs at some degree, wouldn't it just kill caching performance, since it would need more cache on GPU to store all that data?

the argument isn't stupid, there are examples where the two screens render different 3d scenarios. like nintendoland's mario chase and metroid and COR multiplayer.

So now you're going to say that my entire argument isn't valid because I added a TRUE side note? Yes you're right that sometimes acutal things are displayed, but more often than not, it's things like secondary screens, mini-maps etc. Basically stuff that would generally be shown as HUD. But any ways, let's assume, that for some reason they display actual gameplay of a shooter on both screens, the main screen at 720p and the tablet at 480p, it STILL isn't 1200p! 720p+ 480p is barely better than 768p. let's do the math, 640x480=307200 pixels + 1280x720=921600. Those two together equals 1,228,800pixels. 768p is 1365x768=1,048,320 pixels. Now, I'm sure you're proficient in math and everything, but to make you not have to pull out your calcuator, the wiiu res would be only 17.2% higher than 768p. For reference, you/the OP(sorry I'm not sure if you're the op or not), 1200p is 1920x1200=2,073,600 pixels or 97.8% higher than 768p. So you can talk all you want about how my argument doesn't work, but unless you can offer math to the contrary that's actually correct, you can either accept that what you believed was wrong, or you can go on living in a fantasy land where the WIIU can play games in a resolution higher than most high end gaming PCs can when the wiiU is packing 4 year old tech that costs maybe $250 to the consumer. 

1080p, 720, 60 frames per second, 30 frames... ok I got it that measuring pixels and refresh rate on your tv is important, but you know...

Is the gamepad 480p screen processing running on unicorn tears ?

Am I the only one who thinks that, if a game on wii u runs at 720p@30fps on tv, plus 480p@30fps on the gamepad (when pushing a 3D scene like zombiu) should then be considered a 1200p@60fps, adding all processing together, for common sense sake ? 

Of course if the gamepad is displaying just 2D stuff, only the tv should be considered.

I just want to add that the Wii U streams a 1080p image onto the GamePad's 480p screen 100% of the time even when the graphics are only 720p.

When U use 2 GamePad controllers at a time, the Wii U then only streams 2 different 720p images onto the 2 480p displays, but Nintendo said this will only be use when only 2D sprites are being displayed on the touch screen for 2 players.

So now you're going to say that my entire argument isn't valid because I added a TRUE side note? Yes you're right that sometimes acutal things are displayed, but more often than not, it's things like secondary screens, mini-maps etc. Basically stuff that would generally be shown as HUD. But any ways, let's assume, that for some reason they display actual gameplay of a shooter on both screens, the main screen at 720p and the tablet at 480p, it STILL isn't 1200p! 720p+ 480p is barely better than 768p. let's do the math, 640x480=307200 pixels + 1280x720=921600. Those two together equals 1,228,800pixels. 768p is 1365x768=1,048,320 pixels. Now, I'm sure you're proficient in math and everything, but to make you not have to pull out your calcuator, the wiiu res would be only 17.2% higher than 768p. For reference, you/the OP(sorry I'm not sure if you're the op or not), 1200p is 1920x1200=2,073,600 pixels or 97.8% higher than 768p. So you can talk all you want about how my argument doesn't work, but unless you can offer math to the contrary that's actually correct, you can either accept that what you believed was wrong, or you can go on living in a fantasy land where the WIIU can play games in a resolution higher than most high end gaming PCs can when the wiiU is packing 4 year old tech that costs maybe $250 to the consumer. 

The gamepad resolution is 854x480 gentleman.

Packs way more punch than standard 480.