You sure do love your GFLOPs.
When you compare such similar cards, espcially from the same manufacture, it's a very accurate way to judge performance, go look up reviews of the HD7770 vs the HD7870, the performance is pretty linear, of course I won't go completely ignorant and say that is all there is to it, but it's the best way we have to compare the cards.
If Nintendo's CPU is indeed problematic I think I'd write off GTAV. I cant see Rockstar's already existing disinterest coupled with a demanding game build on an engine primarily optimised for current gen hardware leading to any Wii U port.
Well I think people might misunderstand the tech, obviously the CPU is more modern, and not optimized for the engines being used, prophecy's contact is a complete unknown as well, he could be someone not familiar with different IBM processors, or he could be a plain numbers guy.
Wsippel has estimated the Wii U's CPU to be based on the 470s series and has mentioned that those chips don't support SIMD, but there was one that did, the 476fp, which if Wsippel is right, would give Wii U a CPU that is "3 cores" but 6 threads, @ 1.6GHz-2GHz Out of order, it would be faster than Xenon, but you would definitely have to optimize to really see that, but in no way is that a weak CPU, it's simply different, and depending on the clock speed, could in fact compare favorably to a steamroll "4 core" since it's easy to describe that cpu as a dual core with "hardware hyperthreading" Just look to Bulldozer if you need to know what I'm talking about there.
I hope the Wii U turns into another Wii where all the major third party titles are made for 720/PS4/PC and all the Wii U third party games are quirky, exclusive shit with b-grade budgets.
Why? there is no reason they would need to do this, and I am 100% sure that developers will keep dying off if they can't utilize a true market leader or multiport to all 3 systems.