A useful feature native feature of Chrome is its ‘Task Manager’, which allows one to monitor all Chrome processes and their resource consumption:
Firefox has been slow to adopt parallel functionality, though this is mostly that multi-process mode in Firefox hadn’t become available until recently (at least in non-Nightly releases). One still needs to install this Task Manager Firefox add-on — though I would not be surprised to see if this became built-in to Firefox sometime in the near future.