The December 2011 Popular Mechanics has a review of 12V power drills. They
tested 13 brands, including the DeWalt and milwawkee:
The DeWalt DCD710S, it got a top rating of 5. $160 cut 196 1/2" holes and
drove 171 2.5 inch screws on a charge. They didn't seem to dislike anything
about it except the that the battery "attachment had a fair amount of play".
Milwaukee M12 2410-22 was rated "best overall" and was the only other drill
with a rating of 5. $150, cut 161 1/2" holes and drove 171 2.5" screws.
Interesting, that they drove the same number of screws on a charge, but not
the same number of holes; perhaps, the holes require more work (power). The
said it was very "robust" and the only ding they came up with was that the
"battery could use a better grip surface".
I have Makita 18V, so I can't comment on either brand, but I figured it was
another data point to share. I cut out the article and can scan it if
someone wants to see it for the other brand ratings.