How is SD2K faster than MF?

Since Millennium Force drops 300 feet at an 80 degree angle and SD2K drops 307 at a 65 degree angle shouldn't MF be faster. Not only that; MF's trains are much heavier. There is also less friction with the wheels on the 80 degree drop because (i would guess) that the wheels aren't on the track the whole drop because the train is basically dropping straight down.

http://coasterbuzz.com/forums/thread.asp?ForumID=11&TopicID=4680

Funny the topics titles are even the same. That's a lot of physics!

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If Millennium Force doesn't go upside-down, then how could Mantis?