The top two rookie ERAs in the majors belong to Brandon Webb (2.04) and Dontrelle Willis (2.13). (Minimum 50 IP.) Willis is getting most of the publicity right now, but there is some evidence that Webb is the better pitcher. Pro Player Stadium has the 4th fewest runs/per game in the majors this year (8.25). In Marlins road games, 10.43 runs are being scored. BankOne Ballpark, on the other hand, allows 9.95 runs per game, while DBacks road games see only 7.86 runs per game. So Willis has his ballpark working for him, Webb against him. And you can see this in their home/road splits:

They are both very good. Willis has better K, BB and HR numbers right now, but we need to see how much that is a result of the park over a full season. Right now, I would vote for Webb over Willis for rookie of the year, at least among pitchers.