Here's what I went through when buying my new sails. First, we discussed where I would be sailing primarily, along with a discussion of the boat, and how it sailed on the current sails, as well as what I expected from the sails. That gave us a base to work from as to what cloth and how heavy. Then we got into reef points, cunningham, and loose footed or not. Since I was getting a StackPak, full battens were part of the deal.
We spent a good hour or more, just going over this and the options available. By the time we were done, I felt satisfied that I was getting a sail that would be what I wanted, for what I intended to do. After that, he came out to the boat and THOROUGHLY measured the
rig. Did I say thoroughly? When the sail came in, he mounted all hardware and the sail, and it has been everything I wanted.
Went through a similar process with the headsail, though that loft, in my opinion, was not nearly as meticulous as the other one. As a result, I'm not quite as pleased with the sail as I was with the main. It's still a good sail, but there were some little issues (like putting the UV cover on the wrong side).
It's the loft that makes the difference, not the brand so much. That's my experience.