-- Last Updated: Dec-27-12 1:34 PM EST --
To my way of thinking, I haven't seen any "bad advice" here at all. Trailers aren't right for everyone, and your arguments in favor of trailers over roof racks sound more like a statement of "my way is right" rather than logic. Lots of other people said they prefer trailers, some of the time or all of the time, but in most cases also stated some logical qualifiers.
As far as your reasons for trailer use being so universally correct, they aren't. For one thing, "no overhead lifting" is no reason for a non-disabled person to use a trailer if instead they could use a bit of imagination and ingenuity. I've been loading boats on roofs all my life, sometimes with boats quite a bit heavier than canoes or kayaks, and sometimes on full-size vans. I'm not exactly big and strong, but I AM totally intolerant of doing things the hard way, and know how to modify a rack and my loading technique to make the job easy. If you are actually reaching above your head while lifting the entire boat, you are doing it the hardest possible way, and the logical thing to ask yourself is "why do it that way"? If you don't have the ability to modify your rack to make the job easy, then using a trailer may be a good choice for you, but it's not the only way to make boat-loading easy.
As far as bouncing goes, any trailer you buy which is not specifically designed for ultralight loads is likely to have this problem, and virtually every cheap trailer will. On such trailers, you'll have to modify the suspension yourself. If you buy a nice trailer (such as special one for bikes or boats that has a nice, soft suspension), it will cost the same putting roof racks on a small fleet of cars. Even with a cheap trailer, you still have to put a rack on it, and the rack will still be fairly expensive if you can't build it yourself. Besides, the OP is only looking to carry one boat.
As far as having the boats "already loaded", that's nice if you have a place you can park a loaded trailer. Not everyone does. I eliminate the inconvenience of loading boats by making my boat-storage methods quick and easy to use. Even my biggest, heaviest boat can be gotten out of its rack and onto the roof in about three minutes, and then all I have to do is tie it down. I don't have to do any heavy lifting at any point in the process on account of the way I designed my storage systems.
You say you can walk a trailer anywhere you need, but that's true only for you, not everyone. Try doing that so you can turn around on a dirt road or a back-woods road that's really steep. It'll take a team of helpers unless you bought one of those terribly expensive specialty trailers, but even then, you are wasting time that you wouldn't have to if the boat had been on the roof.
Overall, I'd say the pros and cons of trailers versus racks have been well described. As many others have said, I agree that which is the better choice is not universal, but depends on the specific situation.