Why the difference in paddle blade shape between river running and playboat paddles? Does the shape make a significant difference?

Playboating blades tend to be a bit smaller, and designed to slice through the water at many different angles. River running paddle blades are a little larger to get more power.

I think this is a good question. I just want to mention that i had a problem with my Aqua Bound paddle and AB is replacing it for me. I am really happy with their service. to get back to the question. I know AB has 2 sizes in their whitewater range, one with a bigger blade and one a bit smaller. The bigger are for stronger paddlers. Apparently for surfing waves you want a faster, bit smaller paddle, while playing in a whole you want a bit bigger blade with more power for bracing and getting back in the white.
But at the end i suppose the shape of paddle blades are more like trademarks really. I don't know, what do the rest of the guys think? At the end of the day you want a lightweight, durable paddle, doesn't really matter what shape the blade.

Playboating blades are USUALLY smaller in surface area and also a little 'shorter' and 'fatter' (lower aspect ratio if you want to call it that). Whereas a river running or creeking blade would be larger in surface area as acceleration and the need for a powerful blade is important. There are no hard and fast rules and what it comes down to is personal preference. Some people say super short paddles are the ONLY way for playboating. Others disagree. Blade size, paddle length, blade offset, these are all down to the individual at the end of the day. I have quite a few paddles now but only really paddle with the latest one. Doesn't matter what type of boating I'm doing.

Blade shape, thickness and design is very important though and can make or break a paddle. How well does the blade glide through the water on a draw stroke is important as is the flutter. A blade that flutters is not a good one
The design aspects are beyond me but I know what feels good to me... Have fun...

Amen to the statements that blade shape, size, and thickness can affect how a blade performs.

I have a pair of old Voyageur Tasman and a Bering carbon-carbon sea kayak paddles. I have a Werner Kalliste Carbon-carbon stick in the same length. All 3 are staight shaft two piece paddles. The Voyageur paddles ( unfortunately no longer made) are the hands down better sticks. they have a stronger and smoother pull, where as the Werner Kaliiste seems to be curved too much at the end and unevenly. The blades on the Bering are about the same size as those on the Kalliste. The Werner paddle flutters, also losing pull at the end of the stroke. Don't think it's problems are just due to the curvature of the blade, but also seem to be related to the re-inforcement configuration in the center of the blade. Have paddled both brands several hundred miles to confirm this and now the Werner Kalliste is my loaner paddle. The Voyageur sticks are also lighter by ounces and the Tasman has larger blades.

Now if I can afford a new whitewater carbon-carbon stick as light as my Sea kayak paddles. Have an old Harmony carbon carbon break down as my emergency stick, but prefer not to use 2 piece paddles on whitewater except in emergencies.