I use snaps for the upper body parts. The thighs are attached to the holsters and just sit against my thighs. They stay in place just fine because of the leather strapping that holds the holsters. I use elastic with snaps to hold on the knees and shins. I don't use any velcro.
I use velcro for the upper armor, and it works A OK. For the lower armor, I use velcro and elastic straps. I haven't had a problem with the system yet.