In the Au Sable River canoe marathon, held annually in Grayling, Michigan, paddles have undergone series of changes. Other paddlers watch - very closely - to see what works best. In the 50s paddles were traditionlly shaped. In the 60s, the blades got wider, some nearly a foot wide.
Verlen Kruger came along, and made the study of paddles knto scientific experiments. Paddles got lighter - MUCH lighter, shorter, and BENT!!! Blades became smaller, about an 8" square with rounded corners. Paddling cadence increased to a faster pace. And rudders began to appear on boats.
I don't race. I have zero interest in paddling more than 3mph. Unless, of course, if someone's shooting at me. Fortunately, that hasn't been a problem - so far. I like the double ender paddles for the extra control ability that they provide. I've been saved, several times, from broaching in heavy winds, capsizing in reflected waves coming in from two or three directions, being swept sideways into obstacles, etc. by having more control derived from simply having more paddle in the water.
Different paddling situations require different gear and techniques. One of these times,, I'll figure it all out. I hope.