The Chrome multiprocess isolation model is really good. Firefox devs have known this for ages (heck, there were demos of a version of Firefox 3.x with a similar model), but could not actually land this model for two reasons:
- it would break all old-style extensions and users were unhappy about that;
- it takes looooots of memory and users were unhappy about that, too.
Now that Firefox has dropped all old-style extensions, there's large focus on reducing memory footprint, to allow moving to this model without costing as much memory as Chrome.
There are still a few kinks to fix, but this new isolation model should hopefully land within a few months.
Also, all sorts of security improvements are much easier now that Firefox dropped old-style extensions. Also, switching many developments to Rust makes new code much, much safer.