MissMeliss ~ In my experience, it is better to clear customs in YYZ than in MCO. If you are clearing customs in MCO, you are first required to pick up your checked luggage to take through an additional security check before sending the checked luggage back on to a turnstile, go through customs and then pick up the checked luggage again.
When we had to do this, it took us an additional hour or so after we touched down to collect our checked luggage from the final turnstile.
We are flying Air Transat for our October trip and I think we may have to clear customs in MCO for this flight. We are definitely NOT going to have any checked luggage with us for that trip!