In Canada, we have a dual legal system that gives an owner trademark rights simply by using the mark, without any registration requirement. Such "common law" rights, however, extend only to the geographic area in which the mark is continuously used, and such rights may be prevented from growing by another's trademark registration.
Perhaps the most important advantage of trademark registration is that it generally confers exclusive rights for the use of the trademark throughout Canada, even though the owner may only be using the mark in one specific area of the country.
Registration is evidence of ownership. In a dispute, the registered owner does not have to prove ownership; the onus is on the challenger.
Use of an unregistered trademark can lead to a lengthy, expensive legal dispute over who has the right to use it.