Pro-tool reviews did a thorough 12V drill comparison

The winner was Makita, then Bosch, then Milwaukee.

http://www.protoolreviews.com/buying-guides/best-12v-cordless-drill-roundup/25102/

Edit: I corrected this. I only read the graphs, which made it appear Milwaukee was the winner, but their final scores were different. They ultimately ranked Makita higher due to their subjective scores, which included ergonomics.