When flying US -> YYZ -> int'l, the process is extremely simple: follow signs for int'l connections, a quick document check by a customs officer, no security check or other formalities, and you're on your way.

If you want to leave the terminal, you'd instead follow the signs for arrival, clear Cdn customs and immigration (and obviously you would need to clear security again before your flight).

Whether it's worth the trouble or a somewhat better dinner is debatable IMO.