Really a matter of personal preference and what it is you are splitting. If I'm splitting ash or straight-grained Oak, for example, I'll take a good splitting axe all day (dont even bother using a felling axe or a general purpose axe). It's also a matter of technique.
Also, the splitting force generated is proportional to the square of the velocity. It's only linearly proportional to the weight of the splitting tool. Since I can accelerate an axe much more quickly than a heavy maul, I get better results with one. In my younger days, maybe I could deal with the higher weight of a maul and still get good speed. Not much chance I could keep that up for a long session of splitting these days.
I only split about 1 cord a year by hand anyway. The rest gets done on a hydraulic splitter. The gnarly pieces get set aside either for the splitter or burnt whole in the campfire