Box after box of fly line lies on the shelf. But are they really different?
Taper diagrams show where the line weight is concentrated. A quality fly line is much more than taper, though. You should choose a fly line for both the type and location of your fishing. Select a sinking fly line to carry a fly 20 feet deep in a lake when fishing a drop off. A floating line is the best choice for fishing dry flies in a shallow riffle.
Line type also affects casting. Most people think a double taper (with the same taper on both ends) is easier to roll cast. Because of the weight distribution in the tip, these lines seem to load the rod better during roll casts.
Everything in a fly line from the center material, weight, and specific gravity can influence how the line fishes.
If you think your rod is high-tech, watch the video from Rio that explains how they engineer a fly line for the best possible fishing experience.