John McCain's VP

Considering John McCain will be the GOP's Presidential candidate, many speculate who he will choose as his running mate. Among possible vice presidential front runners, Minnesota Governor Tim Pawlenty and Mississippi Governor Haley Barbour are consistently named. The question becomes which would help Senator McCain more? Pawlenty is seen by many as being a moderate, but he is young. Barbour is very conservative, and he is known as the Giuliani of Hurricane Katrina. Many Republicans feel President Bush handled the Katrina fiasco poorly, so Barbour is seen as someone who can competently deal with such issues. Which candidate would help Senator McCain more? Are there other candidates that would better suit McCain?