I would tend to disagree, as every one of my customers that has gone from a 3 speed to a glide have all slowed down. This in 600-750hp, 2800-3200lb combos.
Nine times out of ten, a 3 speed will be quicker in a car--unless the car weighs 1800 lbs and makes 1000hp. Notice how I said car and not dragster, altered, or roadster. :)
(Disclaimer: this is just my opinion, and my experience over the last several decades).