comex's statement is correct. Chrome/Chromium was designed from the ground up for fine-grained sandboxing of renderers and extensions; Firefox's single-process design currently prevents it from implementing any similar layered defense.

Mozilla acknowledges as much with the mission statement of their Electrolysis project:

https://wiki.mozilla.org/Electrolysis

Hopefully Firefox's situation will improve in the near future—at the very least, we'll all benefit if Chrome has a viable competitor. But in the meantime Firefox absolutely is behind Chrome in the security department.

Until Firefox tightens their sandbox, I believe any exploit can still use system calls to directly create TCP sockets.

Chrome forces sandboxed processes to use its network stack; if that's been configured to use Tor, it shouldn't end up revealing your IP and therefore identity.