[quote]Double blade is good if paddler is poor or slow at switching or lacks the discipline to maintain the shorter stroke, quick cadence and fidelity of force direction required for efficient use of bent./quote]

  I agree with everything you say but some people are poor paddlers because like me they only get to go on a canoe trip once maybe 2x a year if they are lucky.

Where I live in SE Mich, a canoe isn't the watercraft you want for the local lakes. Kayak/Fishing kayak will get much more use.

By the time the paddling season rolls around I have virtually NO muscle/paddle memory. With the double and least for me, I can get into a half-way decent rhythm much faster than with a single/bent shaft.

I went to the double because I want to go farther/faster than I could floundering with the single.  The tradeoff is it is much harder on the body
so that' why I do the weighted work-outs I do.

I could have never taken some of my longer trips just using a single paddle. My next major purchase will probably be a carbon-fiber shaft double paddle which will ease the strain on my upper body.

A double paddle isn't for everyone that's for sure.