If I were shooting fixed broadheads, I'd lean toward the helical 5". If not either the 4" or 5" would be fine. I would still stick with the helical though. See the 5" helical will stabilize your arrow the best given your choices. And with a fixed broadhead, I would want the most stable arrow I could get. If you are going to use mechanicals or just shoot field points I think either would work. I prefer helical feathers because they will spin the arrow more then a straight fletch. They will also provide more drag.