0% Water Absorption - a quick false cast or two and your fly will be bone dry by the time it hits the water.
Non-Stick Material - In the summer months you can have a ton of algae and other green stuff in the water. It can be a nightmare cleaning the fly of all that junk. With synthetic, you don’t have to worry about that.
Natural Floating Property - Seriously, these things float, no floatant of any kind is needed.
Extreme Durability - Synthetic is much more durable than natural. You will catch fish after fish on the same fly, no problem.
Trim to Size - Say you’re fishing a specific hatch and all of a sudden you have refusal. Maybe the fly is too big and you don’t have anything smaller with you. Just grab your scissor, give a quick trim, and you’re ready to throw that fly back in the water immediately. You cannot do that with natural material.