Roger, Roger, Roger... where did the science go!? ;P
As you know, I've done a fair bit of canoe tripping. All of it has been with leather boots. Lots and lots of walking in rivers, jumping out in water at portages, etc. Years of doing so in multiple boots. No cracking or other destruction of the leather from all that abuse. They do smell funky after walking through swamp water. But I think synthetics would, too. They don't dry quickly, but then any lined shoe or boot seems to take forever to dry regardless. My favorite waterproof footwear is just a solid leather unlined boot. Keeps me dry, breathes great.
Of course, I am making the switch to Hard Rocks now...