This is more of a love letter than a fight to the death. I just can't get enough of either of these beers this winter. Both have similar profiles to me--hoppy, bitter, and robust--and are incredibly drinkable. FIS is a beer I like more and more every year that I have it. I did a 3 year vertical recently and it ages pretty well, too. The fresh and the year-old bottles were equally delicious with the two year old bottle a little less so, but still enjoyable. Narwhal is the first beer from SN that has really wowed me. I got it on tap originally not expecting much and had to immediately go purchase bottles. I'm on my third 4-pack now and find it difficult to hang onto even one or two for aging. Overall, I might have to give a slight edge to FIS, but Narwhal has an advantage in being a little cheaper and easier to come by. Both are two of the best imperial stouts out there, barrel aged or no. On a side note, I hope Bell's decides one day to bottle their Dagger Imperial Stout since it's another great example of a hoppy IS.