Most trucks and many older cars and SUV’S come with leaf spring suspensions from the manufacturers. The question over which is the better suspension has a long history. Leaf springs have been around for centuries while coil springs for only a hundred years. Both have proven their respective advantages. Which is better will always be a point of contention, but the answer largely boils down to the intended use. A leaf spring suspension is made of a series of long, relatively thin sections of spring steel metal attached at both ends to a frame and suspending the axle in the middle. Coil springs look just like one imagines a spring would, and sits on top of the axle or lower control arm and the chassis
In terms of function, leaf spring suspensions are much simpler, since the axle is suspended by the spring, and does not require the complicated suspension geometry of the coil-spring set-up. Leaf springs are also much sturdier, and are capable of handling much higher loads with less deflection than coils.
Coils spring suspensions offer more range of suspension movement, and allow the user a wider turning envelope through the suspension range than leaf springs. Practically all high performance applications use coil springs. Coil spring suspensions usually perform better, having better engineered geometry than leafs.
For heavy, hauling or budget-limited applications leaf springs should be considered the rear suspension of choice. By design, leaf springs used on pickup trucks are the ideal suspension as most of these vehicles are used for load carrying applications However, there are only a few applications which will benefit from leafs compared to coils.
The two main drawbacks to a coil spring suspension are load-bearing. Cost isn't so much an issue, if the vehicle was originally equipped with coil springs, retro-fits can be very expensive and time consuming. Coils are not generally favored for heavy load carrying, as the coil on axle setup isn't nearly as stable or strong as a leaf spring.