This add-a-leaf kit will lift the rear of your F150 by roughly 1.5" to 2", and a rear block would not be required. Neither method is inherently "better". Add-a-leaf kits are nice because they give you lift and load support, but they also tend to stiffen your ride by a bit. Rear blocks are nice, since they don't change your ride much at all, but they don't give you much benefit other than the ride height.