I and my extended family (95 yr old Grandpa to 28 year old son) live on an island and we are up to our eyeballs in boats(5), motors(5), canoes(3) and kayaks(7) and one stand-up paddle board.  :o  So far this spring we have had 3 motors repaired; the old small 10 hp motor the only one not needing attention.  Our smallest boat is a 14 foot light weight aluminum fishing boat which is actually more unstable than a canoe for being tippy.  We seldom use it.

I agree with solotripper, it depends on what you do most in your water craft (fish? sight-seeing? traveling) and who and how many persons might be coming along with you.  I would pick the one you would use the most and factor in repairs, gas, trailering and storage, and what you would do if your craft broke down.  Unless it is a very nice day even an 18 foot fishing boat can be impossible to row anywhere if the motor breaks down.  Kayaks are difficult to fish from.  Personally I find the canoe/kayak the most dependable transportation simply because unless your arm is broken you will eventually make it to your destination at minimal cost.