You start apropriating electoral votes by percentages and you'll confuse hell out of the government school graduates in Arkansas and West Virginia. Nope, appropriation by district will be easier and cause less confusion. Besides, the district where I live has had a democrat congresscritter since, I believe, shortly after Reconstruction (if fact, it's algore's old district) and President Bush carried us about 60%-40% in 2000.
However, it would help to prevent that popular vote and majority of the Electorate College go to different candidates.