MTI, NRS and Kokatat all make good pfd's. MTI should be easy to find at most sporting good stores. Make sure the arm holes are large enough that you do not chaff. The better vests will allow you to adjust the fit at your chest, shoulders and waist. You will want to try them on then have someone grab them by the straps and attempt to pull it off. If it gives too much it is not a good fit. In water you will find that the pfd will want to ride up on you.
A vest pocket is nice for those items such as bug dope, sunscreen, chapstick, etc.
If you are renting a canoe from an outfitter they do provide ok pfd's. You might look into getting yourself a good paddle that fits. It will make a world of a difference by day's end. Lastly, if the pfd is not comfortable you will eventually find yourself not wearing it.