Why not both?
For the last several hundred years both the horse and rider have been sacrificing comfort for style.
A true good saddle fit is very hard to achieve since the horse moves and the composition of their back changes with all of their movements.
So it would appear that in general the horse world has all but given up on trying to make something that considers both the horse and rider in its design.
Let's Start with the Horse
This is what the System X flexible panel system and the trees that they are mounted to have achieved.
A saddle that is both comfortable to ride in all day and comfortable for the horse to carry the saddle and rider for that same amount of time.
For those that do a lot of hills and ride in western saddles, have you ever come back from a ride and found a puffy spot just behind where the saddle sits?
Or when palpating their back after a ride find that they are tender just before the croup, the area just behind the saddle's jockey and skirting?
This is due to the horse using their rear end to climb those hills and descend them. So what does this mean?
No part of a saddle should ever lay cross, restrict the movement of or put any pressure on the spine of the horse.
Even if it is just some skirting leather, that is still rigid enough to cause pressure points, rubs and soreness.
I can hear the next question... So how can we make a western saddle with a frog and a skirt, since they appear to have to lay across the spine.
Look closely at the pictures of the Working Trail Saddle.
When looking at the saddle from the rear notice the panels are part of the lower skirting. The top skirt with the frog behind the seat is still across the back of the horse but independent of the panels below it so nothing touches the spine.
But what about the Rider?
The way this saddle is assembled it then gives it the appearance of being close to the horse, except when viewed from the rear.
The panels are covered with leather so they will look like every other western saddle.
In fact, with these leather covered panels with fleece on the underside just like every other western saddle out there.
May be used with a thin saddle blanket pulled up in front for wither relief and slightly along the spine so as to not bind or prohibit any movement or air flow down the spine.
NEVER use a solid pad across the back, the pad will inhibit the functionality of the saddle's panels ability to conform to the horse's back.
But English Saddles Provide Spine Clearance
Some will say that with English saddles they are built with a lot of spine clearance and they don't have any skirting or a jockey that will cause pressure across the spine.
Many don't realize that while English saddles look significantly different than western saddles.
When you remove all the leather and flocking their trees while smaller, are very similar in design. Starting with their four pressure points that are sculpted and angled to fit the horse the best that it can.
Flocked to help distribute the weight and the pressure points. In many ways the English saddles do this much better than western saddles, if the rider re-flocks regularly to the changing shape of their horse's back.
An ill flocked English saddle is just as harmful as any other fixed tree saddle.
English saddle fitters will start with a bare tree on a horse's back just as a western saddle fitter would. Making sure the bones of the saddle fit the horse at rest.
So Now What?
A fixed tree will never be able to truly fit a horse through all of their gaits. The back of the horse just changes too much for a fixed tree to be effective.
Don't think that English saddles are the only ones that attempt to do alleviate pressure points. All styles of saddles and riding have been trying to do this with different pads, some attempting to distribute weight and pressure.
I have seen more saddle evolution in the past decade than I did my first 30 years in horses. This refreshing from the horse community and I applause them for making these steps.
Look at the thermographic image of the pressure exerted by the System X panels. The even pressure along the whole panel.
Something you can feel when a System X saddle is placed on a horse with someone in the saddle.
Begin by running your hand under the panels of the saddle and feel for yourself, that while you feel pressure.
Notice it is not pointed nor is it focused in any one small spot.
Now put the saddle you've been riding in for years with it's pad, on the back of your horse. Have someone sit in it for you, then run your hand under the pad along the back of your horse.
The pressure changes significantly as your hand moves under the points of the tree or the seat of the rider.
What About No Tree at All?
Treeless saddles while they address the issues with the fixed tree.
Putting significant pressure across the spine since there is no tree to hold the rider up off the spine.
For the well balanced rider this doesn't pose nearly the issues. Compared to an unbalanced rider, shifting their weight that tends to go against the movements of the horse.
These all cause the horse to compensate, straining muscles while some one sits on them in an awkward way.
Consider the patience and tolerance of the horse you have been riding in your current saddle.
Recall all the other horses in your past that just seemed 'unhappy' under saddle. Could it have been the saddle?
If you ever would like to feel a demonstration like this.
I have a tolerant horse that will allow us to do this.
I have a horse-like saddle stand that it can be shown on.
If you'd like me to demonstrate on your own horse against your saddle. We can see if we can arrange something depending on your location.
I'll bring a saddle of your choice to demonstrate with or similar style, they all possess the same flexible panels.