Buying a saddle for your horse is not a snap decision, or one to make purely on aesthetic tastes. There are many saddles to choose from, and the differences between saddles lie mainly in the tree. Before you even begin to fit the saddle to your backside, and to your horse's back, you have to learn what makes one saddle different from the other so you can get the best saddle for your purpose.
The first choice is an obvious one: English vs. Western. They are two completely different types of saddle trees. Your desired use usually determines the type of saddle tree you start out with, but if you are looking for a long-lasting saddle your horse will wear comfortably all day, Western is the better choice. It distributes your weight evenly across a greater area on its back.
Type of Saddle Tree Forms
Both English and Western saddles have a base form deep inside the outer leather you see when you look at your saddle. Those forms are what make the specific size and shape of the saddle. Saddle trees are made from two different types of materials in both styles of saddle: wood and synthetic. Wood trees come in three types: the rawhide, bullhide and fibreglass-covered wood. Each choice has a different set of qualities, depending on your needs.
Rawhide trees are durable and take a lot of abuse. They flex better, and the leather casing protects the underlying wood from sweat and water. Rawhide saddle trees use fine leather that the maker puts on the wood form wet so that it shrinks and forms to the tree. It absorbs a lot of stress and makes a great working saddle.
Bullhide saddle trees are made the same way rawhide saddle trees are, except the leather is much thicker. Bullhide leather is from the dense, heavy hide of a bull, which gives it a coarser, harder texture. That difference makes the bullhide saddle tree stronger and more resilient to impact than rawhide trees. Bullhide is used in most premier leather saddles because of the strength and, although thicker, the density of the leather gives it more flexibility to mould to the horse's back easier than rawhide.
This type of wood saddle tree covering almost bridges the gap between wood and synthetics. The fibreglass resin sprays on evenly over the wood to form a strong, unyielding barrier coating. The inner form is still made of wood, however. There are a few drawbacks to fibreglass resin. The coating is so strong it is less apt to mould to the horse's back. A proper fit in this type of saddle is very important to prevent back strain. The biggest benefit to fibreglass is the cost. It is not as subject to the whims of the economy as leather is.
Ralide trees are a completely synthetic, non-wood saddle tree made from a form. These trees are very economical and come in a wide variety of sizes. They are less flexible than wood and leather saddle trees, so may not give you the best overall comfort, or ride duration.
A single variation on all of the above saddle tree materials is the flex tree. This saddle tree defies the old saddle style need for sizing because the tree is made in two parts with an adjustable lever on the outside of the saddle so the tree can move in and out as needed for each horse. This type of tree fits all horses well, but none of them to the degree of a custom fit. It allows riders to easily switch from one horse to another while having only one saddle.