An application for divorce, with or without a claim for property, must be filed at the Ontario Superior Court of Justice. All other family law applications can be filed at the Ontario Court of Justice. As long as you ensure you are filing your application at the right Court, you are free to choose a Court location on the basis of where you reside, or if your application includes child custody and access issues, where the child resides.
If your spouse contests your application for divorce, you will be required to regularly file pleadings and make court appearances. Choosing a Courthouse where you and/or your child resides (if applicable) will make these events less burdensome. Location may not be as important however, if you are filing an application for an uncontested divorce.