my friend has a handful of duis, and got out of more than a few, and here is his lawyer's advice:
never blow, always opt for the blood test. you have the right to choose.
1. it takes time to take you to the designated hospital they draw blood at (longer wait = less BAC)
2. once you get there, they make you wait a little longer
3. after they've taken the blood, there's a chain of custody, and everyone has to sign off on the blood sample that handles it, increasing the chances of someone fucking up
if you go blow in the breathalyzer at the jail, your fate is pretty much sealed.