Jacket thickness, metallurgy, hardness of lead, lots of variables on how bullets perform. I'm not a Hornady engineer so I can't speak to exact specifics as to why its scientifically better but my sample size of about 1500 or so coyotes I've killed in the last two decades with various Vmaxes, the 53 has hands down outperformed the 50s and 55s. I've had way more splash wounds (mostly 50s) and runners/spinners with the flat based 50/55 than I have the 53s. The 53s rarely splash when hitting shoulder bone and when/if a bullet does exit its usually a small hole. They are very consistent lot to lot and have shot outstanding in every experience I've had with them. Being boat tail they are also easier to load than a flat base bullet.
If you haven't tried them I strongly recommend them, only thing to be aware if is they are longer and may not stabilize in a 14tw barrel.