Immigrant Visa - Getting Married before or after entering US

Hi,

Assuming I am living currently outside US and I've Immigrant visa with six month validity to enter US. I understand once I land in US, my passport will be stamped with I-551 stamp which is a temporary green card and I will get actual plastic green card within few months in the mail.

Now my question is about marriage. If I marry before entering US, will it take more time to get my wife visa as compared to once I've green card and I marry to a girl living outside US? Or it does not matter in terms of time to get my to-be-wife visa.

Please comment.

Thanks.