It's all related to the type of engine and cams that you have and the type of driving you do. If you have a low-rpm, high torque engine (stockish 5.0) then 3.27 may be okay for a DD. A DOHC, 4.6 (Cobra, Mach 1) high-rpm, high HP engine will do better with 4.10's.
Gears alone will not make...