Below is an image of the different shapes of the stick movements.
Top row, from left to right, is circle, square(-ish), and (old school) square.
Second row, left to right, is hypothetical octogonal, cross (aka plus), and diamond.
Supers and 360 are circles
Compititions are square-ish
Oscar's 4 way restriction plates are cross (at least the model I have)
Trons original was diamond
Old apple II joysticks were (old school) square
Almost all current "squares" are really the square-ish shape.
FWIW, I don't fight too much, and like the supers a little more than the comps. My very minor irk with the compitions is I can feel the diags but can't feel the "straights"; it feels "unfair". The hypothetical octoganal shape would be able to feel both the straights and the diagonals, while still being circle-ish.