I can tell you from experience that the difference between a canoe and double kayak is black and white. Some good, Some bad.

Handling - I built Nicks double, and it handles well, very very stable
you would have to try real hard to dump it.

efficiency - The double really shines here, on a trip earlier this spring, we had two doubles and a canoe in the group on a multi day trip. The poor canoe had trouble keeping up to us, especially in a wind, it seemed were waiting for the canoe to catch up most of the time. I found we could go along way with little effort.

Tracking - straight as an arrow!

paddle solo - Yes it is feasable to paddle solo from the rear cockpit, I do it all the time but you need a rudder if the wind comes up. and you won't have any problems turning, with or with out rudder.

Storage - Canoe wins hands down. It's a pain to pack a kayak for long trips. (sorry guys/gales, but it's true)

Portaging - Canoe wins again.