Your firefox image is considerably narrower than the safari image, so the results you see aren't surprising. Are you on OS X? OSX has strange window sizing behaviour, and Firefox on OSX doesn't have the aggressive chrome minimization it has on Windows (or at least, it didn't used to, haven't checked recently). Your results will be much more comparable on Windows or Linux.
That's a much more modern theme which behaves much better at different browser widths. It's still fairly alpha, not all Hobo components are properly styled, but it's pretty nice.
cheers,
Bryan