it depends on your horses back and your preferences while sitting in the saddle.
make sure you let someone professional help you choose because it can not only make your back hurt after some time, it can also cause really bad back issues on your horse and also make it unhappy while riding.
Horses tend to be more picky about a dressage saddle than others. Of course the saddle needs to fit you, but you also should ride your horse in it before purchasing it to see how they like it:)
When buying a dressage saddle, you need a saddle that both fits well for your horse and for you!
When I sat in some dressage saddles recently- I felt uncomfortable, my leg cramped and my hips hurt- a perfect example of the wrong dressage saddle!
I'd suggest trying out as many as you can until you find one that's 'just right' for you- and then finding out if you can get one to your horses size- or have it custom made!
I would have a professional sellier fit it for you or ask a tr