You may want to learn about the different parts of a canoe that would affect how it is used. I have been a whitewater raft guide, video kayaker, and whitewater kayak instructor (ACA certified) on the New and Gauley Rivers in Southern West Virginia since 96'. Now keep in mind that all of my experience is with Class III-V+ whitewater so I have little experience with rec-touring boats and there is a world of difference.
Here are some design terms:
Rocker: This is the banana shape of a boat as viewed from the side. the more rocker, the easier it turns. You would want more of this for whitewater applications and less for flat water. The con of having more rocker is the boat becomes difficult to keep it going in a straight line and you will have to compensate more with paddling strokes such as the J-Stroke.
Tracking: This is the ability for a boat to glide in a straight line. This comes in handy for crossing large bodies of water. Again, this is what you want for lakes and flat moving water. Boats that track well do not have much rocker at all and may have a keel.
Keel: This is not found on whitewater boats because it is used to improve tracking. It is simply a ridge of some sort.
Just my 2 cents:
I have used plastic kayaks all over North America and have run everything from large rivers to steep creeks where hitting rocks is a fact of life. I have had boats fall off of vehicles and bounce down into canyons and I have dragged boats for many miles while carrying out of remote gorges. The point I am trying to make is I have never had one crack. Plastic does not glide through the water as nicely as a hard material such as fiberglass or aluminum but it is darn near indestructible. If I was to buy a canoe, I would want to decide if the majority of my boating would be solo or with another person, what I would be carrying, the type of water I would mostly be paddling, and how rough I plan on treating it.