If you go to the Newfound Rendezvous, you can check out my kayak which is flat edge and the joints are as tight as it gets and it's 4 years old.

I built 5 with flat edge and experimented with cove and bead with one. For certain parallel runs without too much twist (like a canoe) C & B is nice and works well. But for twists and more extreme bends, i feel it's counter productive and if you sand in a little too deep, you are opening up gaps. You also have the chore of tapered ends with C & B.

I found milling good C & B strips very dependant on strip thickness, which means you now added another major time and care stress into the process. Many times I use strips cut years ago along with new ones and I would ultimately have to run them through a drum sander to get the even thickness to have a C &B set-up work easily.

There's certainly a lot of beautiful kayaks using C & B - but I find it not necessary. I don't like making strips and the easier that part is the more I enjoy the actual building process.