Green is one of my eternally favorite colors. In my opinion, most mixed greens lack greeness, if that makes any sense. The best greens are already made, and then modified with other colors, such as the addition of more yellow or blue, or even red. The clarity of viridian, Hooker’s, and sap just have a lot to offer.
Traditional greens are mixed from yellow and blue, and in watercolor, you can use cerulean and cadmium yellow, burnt sienna and ultramarine, and all other yellow-blue combos. Some pigments are more “settling” than others, which can be more transparent, and this will affect the final color quality.
Maybe I just need to work on mixing them more . . . but can you really get such a clear green as sap?