Good question, Zeb.
Historically, the VP choice is as "political" as it gets...it's meant (mostly) to attract a certain segment or segments of the Electorate; OR to "appease" a certain segment of the electorate/and or the Party.
Therefore, the VP choice will depend on a) who the nominee is and b) where the electorate appears to be entering into the general election.
Perry may, or may not, be the "best" choice leading into the election.
Much like Palin; I think Perry is "playing it coy"; and waiting to see how things go.