I use both. Sometimes I use both on the same head. Many of my head colors start as powder, but have glitter and perhaps some hi lite added to the base color. After doing the powder coat, I will dip some of the colors in clear or transparent vinyl colors of roughly the same color, then they get the oven at 190 degrees for a couple hours. The result is one tough head color. The top vinyl coat over the powder paint brings out a whole new world of color depth. Some of the colors I have shown here.
I don't make claims about smashing the heads with a mall since I think that any finish undter those conditions will crack....the lead will compress way too much for it not to. Just my opinion here. The vinyl tends to be more flexible though even after it has dried thoroughly. The powder tends to be more brittle, especially after heat curing. Again, my opinion.
Another thought here is that any head finish's durability will depend a lot on how the heads are kept ready for fishing. My walleye heads go into a plano box where each compartment has a foam bottom and a foam top piece. My small heads used for panfish and crappies go into pocket boxes designed to hold individual ice baits and these boxes also get a foam divider added to separate the two sides when closed. Heads get far more wear put on them rattling around loose in tackle-box trays than they do in the water. If you're going to put a finish on your jigs, take time to keep them protected until you're ready to use them. And as always, just my .02.