3-button controller dpads
I took apart two of my Genesis controllers to wash them when I found out why one controls much better than the other. The dpads are completely different.
Left="good" pad, Right="bad" pad
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The controller on the left has the type of dpad that's on the 6-button controllers and Sega Saturn controllers (where the dpad and the white part "sandwiches" the casing). It controls much better than the one on the right, especially when hitting diagonals.
The "good" controller also has the case/buttons in matte black and has a textured feel, compared to the "bad" controller with it's glossy case/buttons and smooth feel.
THREE VARIANTS OF 3 BUTTON CONTROLLER
The one on the left is my favorite 3 button as well and my least favorite is the very first Genesis controller, the one with the red markings on it, the one pictured on the right is identical to the original 3 button other than the red markings as far as I can tell but is much nicer to use.