Dontrelle is a charismatic guy, so I can understand the sentiment to want him to have won it, but he didn't have the better year.
Carpenter: 7.93 K/9, 4.18 K/BB, 1.06 WHIP, 151 ERA+, .623 Opp. OPS
Willis: 6.47 K/9, 3.09 K/BB, 1.13 WHIP, 153 ERA+, .644 Opp. OPS
ERA+ is park adjusted, so that corrected some of the advantage of pitching in Miami, which is why Willis' margin over Carpenter isn't as big as it would be with their regular ERAs.
Of course, Clemens did this......
7.88 K/9, 2.98 K/BB, 1.01 WHIP, 221 ERA+, .544 Opp. OPS
Houston got shutout in 9 of his starts, which is why his W/L record wasn't spiffy enough to get him some real consideration. I'm all for using W/L record as long as it is expected wins from Baseball Prospectus, which corrects for run support, defense, and park factors.
EDIT: added Opp. OPS