I have the Nord-Locks on mine and have been really happy with them. I can see how safety wire or stage 8s are another step above that, but that's also getting a lot fussier for install.
The torque needed to unlock the Nord-Locks and take the bolts out seems to be about 2-3x the amount you torque them down with, they hold really well. They are also reusable, and available locally more easily than Schnoors.
Once the ramps are locked together, they have to be spread apart to loosen at a different rate than the bolt pitch, which is what makes them hold tighter than a teeth only solution.
One thing to note if you think of switching is that they are thicker because of having two halves, and may require longer bolts. (Good to switch to new ones anyway)