Which Shape Guard Gives the Most Power?

I love my new power soccer chair although I guess it really isn't new anymore. Anyway, another thing I love about it is that it came with a metal guard. However, I'm starting to think about metal guards and what shape produces the best power from a physics perspective or if it really matters. Let me give a rundown of the different types.

The type of guard that I use is produced by the Power Soccer Shop and is sold for $399.99. As you can tell, it has a flat front with rounded corners and flat sides. Personally, I do enjoy using the guard as it is easy to control the ball while going forward.

This next type of guard is produced by the Kick It Shop and is sold for $399.98. It looks very similar to the one I use except for it has sharper corners. I think that it would work very well because personally when I used to play with a plastic guard, I liked having square corners because I felt like they hit harder.

The third type of guard is also produced by the Kick It Shop and is also sold for $399.98. Personally, I think that this guard looks great for an experienced player. I feel like it might be hard to control the ball at first because the rounded design might make it easier for the ball to slip off while dribbling forward. However, the rounded front also allows for several shots at angles that a square guard could not make which is definitely valuable and unexpected.

So, I have no idea if the design matters at all in the power. It may be as simple as the different types of metal used. Can anyone float some physics knowledge out to inform us all about what shape, if any, would allow for the most power with a similar shot or spin?