In addition to my Old Town, I have and old Mohawk canoe. Smooth bottom (no keel), oil cans like you wouldn't believe. Great initial stability, very good secondary stability. It's length is around seventeen feet. It is really good for two paddelers, awesome for one. Sharp entry and quick responsive. Put a load in it and it turns into a different boat. Doggy on the flip and won't track worth a darn.
A good traveling canoe doesn't really make a good cargo/packing canoe. Similar to the difference in tug boats and speed boats.
Tripper canoes are a careful balance between both and perform best when longer than 18 feet, better at 20 feet (my experience anyway). As has been said, some rocker is good, but too much and the boat can be unresponsive loaded down or even lightly loaded but unbalanced. Tumblehome (wider at the waterline than at the gunwales) is good for initial stability, but will decrease secondary stability when the canoe is loaded down.
No one canoe will do everything. The boat to run class III rapids can get you hurt when loaded with Moose quarters on calm water.
Shoot the gap. Find the best compramise of qualities and error on the side of stability and durability; don't worry about the weight of the boat. Canoe wagons and portage carriers are easy to build. With them, you don't even have to unload to transport.
Of course all of this is my opinion and based on my personal experiences. I am not a whitewater guy. I have run a few rivers but not any that would count as anything above Class I. I hunt and fish out of my canoes and have boats for this purpose. I have built several stitch and glue type and had a blast doing it. I'm not sure building one is really any cheaper than buying one out-right. I do think building versus buying, you can get a better boat for the same money. Besides, it is a lot of fun if you are a woodworking kind of fella.
A lot of the fun of a boat is picking one out. Here are some photos and a link to what I think is my next project.
Butler Products Freight Canoe