A figure 8 safety clasp requires one extra step to open: unhook the loop, then the primary clasp releases. Measured against the security benefit, most people find that exchange easy to accept.
Visually Speaking
Push button and lobster clasps offer comparable security through different mechanisms. The push button opens via a flush-surface button that triggers an internal spring, keeping the outer profile smooth. The lobster clasp uses an external lever tab that sits proud of the surface.