They are not all the same shape and I am sure very in construction.
Like color and wheels, appearance is subjective. My preference is for Kirk Evan's rear wing as it has less of a delta shape and the ends follow the curve of the body. IMHO, this make the unit appear more cohesive with the car's styling. This wing was stock on the Amerisport GT5s, but, not those installed at De Tomaso.
I believe Kirk now has a thinner, lighter version on the same theme as his original.