Two more cents of input.
Once you get to water, canoes are great (both flatwater and ww). Neverthe less, I know many that will no longer drive with a canoe on top or on a trailer. They are long and typically deep. They can really be scary on the rig (and water) in bad winds which seem to follow me wherever I go. My buddy sold his canoe after a bad experience traveling with it on top of his pop-up trailer.
What kind of bad experience did your friend have? I have driven probably 50,000+ miles with a canoe either on my car, truck or trailer and have never had a bad experience of any kind. I've driven thousands of miles with 2 or 3 canoes on top with no problems. The canoe needs to be securely fastened to a rack which is in turn securely fastened to the vehicle but I would not think twice about setting out on a multi-continent trip with a canoe on top of my vehicle.