The point is, you'll wind up with a boat that is stronger, lighter, faster, looks better, and is more satisfying to paddle than a commercial boat, and you'll pay a helluva lot less for it. I don't know . . . In order to fully understand the advantages of homebuilding a sea kayak, it'd help to understand a few terms used when describing a kayak design. A kayak is described in terms of its length, it's waterline length, its beam, and its weight. The beam is the width of the boat.
Stability is the tendency of the boat to roll or tip while in the water.
A boat with high initial stability will be very resistant to lateral heel, but when it capsizes it does so with no warning. A boat with high secondary stability may be tippy at first, but as it heels, the resistance to that heel increases. But it helps to understand them and how they fit your personal skill level and intended uses or desires. Generally, I'm refering to boats built of wood and covered in fiberglass cloth. Stitch and Glue boats are generally made from Okoume marine plywood panels cut to shape and then glued together using marine epoxy.