Having done both, I would say that canvas is really easier to apply. If you don't like the idea of putting tons of weight in the canoe, try the upside down approach. I personally prefer this method. Simply make a couple of supports the same width as the gunwales at the support points and put your anchors for the stretch down low. Once you have all the equipment (come along, "clothes pins" to hold the canvas, large scissor like clamps to attach the ropes or chains to the come along, staple gun with SS staples etc. The job goes very easily and much more quickly than dacron. The down side is that you have to wait at least six weeks for the filler to harden and cure. The filler itself is very easy to apply.
My first experience with dacron has not been a particularly happy one. After many weeks, when exposed to cool overnight weather, the dacron loosened and formed many blister like pouches on the sides of the hull. I just finished going over the entire hull with a hot iron and they disappeared, but I'm afraid they are likely to come back. Time will tell. My first experience with canvas went off without a hitch. There are some very good photographs of the upside down method in Jerry Stelmok's book about Joe Saliga (available from the WCHA store.) The dacron was fun to apply, but took much longer than a canvas job. Many others have used dacron without a problem. I believe that i did not use enough heat in the shrinking process although the covering looked drum tight.
The real issue is to answer the question "How important is the weight of the canoe?" If you're going to do a lot of portaging, you can save about 10 lbs on the finished weight. If not, I'd stick with canvas. It's much more rugged, time tested and reliable.