The CIE 1976 u'v' chromaticity diagram is skewed to be closer to perceptually uniform, and is probably overall a better picture than the xy chromaticity diagram

The CIE 1976 u'v' chromaticity diagram is skewed to be closer to perceptually uniform, and is probably overall a better picture than the xy chromaticity diagram or than the equilateral triangle picture. X, Y, and Z dimensions are somewhat arbitrary, so plotting xy inside an equilateral triangle isn't inherently more correct than plotting it inside an isosceles right triangle. If you want you can use something closer to the cone cell responses as your coordinates, and the result may be conceptually clearer, but any 2d picture like this is going to be misleading to viewers who don't have a sophisticated understanding of how vision works and what the diagram means.