I don’t think having a brand rep out will be as helpful as an independent fitter, unless you already know/think that a saddle in that particular brand will definitely work for you and the horse and it’s just a question of fine-tuning it. Brand reps (most anyway) aren’t going to tell you that their saddles won’t ever work for you and the horse, and they won’t suggest that another brand will work.
Most brand reps will charge a fee that they then might waive if you buy a saddle through them.
An independent saddle-fitter will also charge a fee, and some may carry a stock of used saddles and may waive a fee if you buy one of those. But there’s less of an expectation that you’ll buy (in my experience anyway), and at the end you’ll have some tracings and some suggestions about which brands and models might work for you.
And independent fitter can also help you evaluate any saddle that you do try out which is very helpful if you’re trying out used saddles. That evaluation costs money as well, but it’s very much worth it.
Don’t forget that you have to fit both you and the horse, so the suggestion to have your coach there to comment on whatever saddles you might try out is a good one.