Difference between Xflow and Standard 2 pass

Hey, I was just wondering what the difference was between say, an Xflow BlackIce XtremeII and a BlackIceXtremeII, I was just wondering what were the pros/cons of having either one, I already ordered the standard 2 pass but i was curious.

This has been discussed heavily lately. Perform a search, or start here http://www.ocforums.com/showthread.php?t=456189

Alright, I just woke up, maybe I should turn on my brain first...