And the most negative aspects of Bush's legacy are fairly constrained to the Middle East
That's a very optimistic statement. And even so, given how everything that happens in the Middle East influences the rest of the world, I wouldn't be so sure about how "constraining".
Also, while it was a longterm process, Bush and his administration had their share of responsibility for an outbreak of the worst global economic crisis since the Great Depression. This is affecting everyone, to various degrees, but everyone.
Nixon at the very least is probably the most evil president the United States has ever had.
I can't argue with that, but the question was "which president was better, or less worse", not "which president was a better human being".
If it was the latter, I would reluctantly, but vote for Bush.