I've seen a lot of rudder pedal design, from simple welded steel tubes to more complex branded aluminum forgings.
They all seem to work equally well in my experience, and I've never found myself wishing an airplane's pedals were a different shape.
However, there must be designs which work better and designs which work worse. Considering how common and uniform flight sticks and yokes are, I'm surprised there isn't more manufacturer consensus on pedal shape. The upshot from the lack of design consensus is it's hard to design through emulation. Maybe ACA did a bang-up job with the Citabria's rudder pedals, or maybe they grabbed something easy to manufacture in the 1950s and it was grandfathered in despite glaring deficiencies.
Is there a resource which could be used to make an informed choice for rudder pedal shape, e.g. a study of rudder pedal shapes vs. performance and user comfort?
P.S. For info, What are specified rudder pedal forces? gives some data for the forces they should be able to take.