I'm not sufficiently familiar with Chrome's architecture to speak comparatively, but Firefox Quantum (57) has a significantly improved sandbox thanks to finally

I'm not sufficiently familiar with Chrome's architecture to speak comparatively, but Firefox Quantum (57) has a significantly improved sandbox thanks to finally going fully multi-process (full status at https://wiki.mozilla.org/Security/Sandbox https://wiki.mozilla.org/Security/Sandbox), and replacing C++ components with Rust prevents certain classes of potentially exploitable issues at compile time.