I wouldn't recommend going double to someone until they were aiming for high lift or something above an LS6 spring rate. (105's are less aggressive than LS6's)

Basically until you are aiming about 130#. At that point, I'd suggest the double. And if you double roller, please ensure the chamfer on the back of the crank gear is machined to meet the chamfer that is on the stock crank gear. Rollmaster etc doubles were made for an Aussie motor that has a different chamfer than the US motor.