I made the switch and
After I switched out my combo knobbie tires to the full street tire... I went from 11 mph for 10 miles avg speed to 14 mph for 15 miles avg speed. So in my case... I ride farther and faster with this tire
https://www.biketiresdirect.com/product/vittoria-street-runner-26-inch-tire?sesgl=1
I also went with new tubes. Cornering traction also improved. No flats yet but the road I ride on gets swept every few days.
My dramatic speed improvement may be the new shoes effect but they are smoother and quieter and lighter andore comfortable ... Well what's not to love? The price is decent too so I feel like it was worth it. I've been able to keep up with some of the slower roadies now once in a while on my citified mtb.