That depends on how you define better. And for pitchers who are not free agents, availability is a little hard to assess. The two most commonly used defense-independent measures of pitching are the FIP (which depends on strikeouts, bases on balls, and home runs) and the xFIP (which depends on (which depends on strikeouts, bases on balls, and fly balls). Because of the DH, these should differ between the leagues, since Ross Ohlendorf is a lot more likely to strike out than Jim Thome, and so forth. A simple regression model using 2010 data implies that FIP should be 0.201 higher on average in the AL and xFIP should be 0.212 higher in the AL. The table below compares a number of available and possibly available pitchers, with AL pitchers statistics adjusted to be comparable to NL pitchers.

If you've been following the discussions you can see why there's disagreement. Duke is an OK pitcher if you like xFIP and fairly poor one if you like FIP. Who is better than Duke also depends on which measure you prefer. Would Bruce Chen or Barry Zito be better (FIP) or worse (xFIP) than Duke? What happens to Kevin Correia when he leaves San Diego? With Jorge de la Rosa and some others, there would be no argument.

These pitchers will also cost wildly different amounts. This year the Pirates are one of the teams with money to spend. As long as the Yankees are not bidding, the Pirates could be competitive. The cheap pitchers all have injury concerns, but they are all apt to get hurt.