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Here is a pair of teeth from your larger reel sprocket:


You can see that on the left side of the recess between teeth there is a very steep slope, but the other side has a much gentler angle, due to the tip being worn or broken away. This happens because the rollers in the chain are further apart than the teeth on the sprocket, so they wear away the sprocket to match the pitch of the chain. As wear proceeds further the steeper side will become undercut, then the tip of the tooth will fall off. When the tips are gone most of the way around the sprocket, it will start slipping.

Here is a pair of teeth from your smaller reel sprocket:


This time you can see that the teeth have splayed out on both sides, resulting in the height of teeth being reduced. On the left side of the left tooth you can see some secondary angling of the tip of the tooth. This reduces the height even faster.