Belying all the physics that go into a paddle and how they function, paddles are largely a matter of personal preference. I've seen pictures of guys paddling along using a chunk of bamboo from a roll of carpet, with sllts sawn in the ends and rectangular pieces of plywood glued and screwed in. Not the "best" - but surely functional.
I make and use only single paddles. If you followed Verlen Kruger's adventures you can see he used only a single bladed paddle, and that was all his life, in all the types of canoes and kayaks and hybrids he used. I've tried both and find , like Chuck, the single blade can get you in and out of the tightest places while canoeing, but that long monster can cause problems. They're fine for some, but I guess I just go into so many creeks and bays that only a single blade works for me.
I make the modified beavertail, from scraps left over from making cedar strip canoes. I've currently got 38 of the buggers. Love 'em and just get a kick out of making 'em. I use the pattern and plans described in the book by Gil Kilpatrick.