[Bill Baer]

I don't have the percentages for you but driving a faster car is a definite advantage at the finish line as said before you always have your opponent in front of you and you can see and judge the closing rate.
However in the 28 year history of the Midwest Super comp Series the same 155MPH (slow) Small block super comp dragster has won 5 championships (3 with original owner& 2 in a row for the current owner)
So being the fast guy might be overrated.