Easy - Which ever shoots more accurate for you. Your bow will not shoot an infinite variety of arrows - there will be a couple of sizes that will simply perform better.

That said, and a lot of variable left out, I prefer hunting with a carbon shaft (compound). They flew great for me, they penetrated great and were tough as nails. I used Gold Tips. With my longbow, I found that a 2216 aluminum shaft flies best, so thats what I am going to use.