Does it make a difference who files for divorce first?
Not really. Under Canadian law, there is no strict legal advantage to filing first. As long as you and your Ex qualify for a divorce under the provisions of the federal Divorce Act (by establishing a “breakdown of the marriage” as that term is defined by legislation), then either of you can file for divorce – there is no procedural benefit for one of you to do so before the other. In fact, in some circumstances you and your Ex can even apply jointly.
With that said, the divorce process can be acrimonious; you may have personal/emotional reasons for wanting to file first, or for wanting to wait until your Ex starts the ball rolling.