I have not paddled the Northwind16 but I have paddled the Magic a few miles and it is a very good solo tripping boat.  I can give you some information on what I have found about canoe size.  First you need to look at what the canoe will be used for and what will go in it.  I weigh 190 Lbs and I carry about 65-70 Lbs gear on solo trips.  I loved the magic until I tried a smaller boat. The Magic has not been on a solo trip since. My new canoe is 15&1/2 ft.  If I were carrying more weight than I am I would want a larger boat but at my load I think the magic good but not ideal for me. I think the larger boat is more seaworthy but not as much as I originally thought. For a longer boat on the crest of a big wave both ends of the boat are out of the water and in the valley both ends are under water and this makes up for higher sides.
So I would tell you to compare your total load to my total load and adjust the size of the boat accordingly.