I like your decision tree for buying a 7" tablet

That claim was likely pure marketing bluff from Apple about the A5x vs. Tegra 3. The Apple CPU is still the same dual core, but with a quad core rather than dual core GPU in place. It's not CPU architecture change like going from A9 to A15 in the ARM world, and the Tegra 3 has a quad core GPU too. That's not to say that Apple's mobile chips aren't fast and they do benchmark very well, but I think it's unlikely that the A5x could be 2x or 4x faster than the Tegra 3!