I think p_p, makes a good observation.
There probably isn't one way to handle this that fits EVERY condition.
I think we agree that getting to shore and into dry clothes or raising core temp is important, but I can see how "swimming" could deplete your core temp enough too cause heart failure.
I've read where they tell shipwreck sailors to pull there legs into their waist to try and hold their core temp up.
I guess that's were the "judgment" part comes in?
Depending on the water temp and your individual reaction to it, you have the choice of swimming for shore, staying with canoe, or you could roll into ball, and in all conditions let the wind and waves work in your favor if possible?
I'd say one constant was keeping your PFD on. I'm sure there's a scenario where being able too swim "faster" without PFD might be a benefit, but I think you could float and survive a lot longer in a PFD, than not make it to shore and exhausted try to tread water sans the PFD?
Ideally you don't let yourself get into this scenario, especially far from shore.
My one and only cold water dump made me a much more cautious paddler

Assuming you survive , hopefully you LEARN something from it?