Torque.. 4 strokes have crazy amounts of torque but little top end RPM. They never really went anywhere after the mild 4 stroke craze in the last 90's.
There were some crazy projects with 4 strokes though. The Mother Thumper was always my favorite..
http://www.rcalloys.com/our_trucks/fourstroke.html
-- John --
1:1.. 01 Z28 Camaro A4 Sure.. its stock.
1:8's.. K3, Inferno GT, and a straight line beater car
1:18.. RC18t Mamba and 3s lipo