If you marry before you land in Canada and become a PR, then your only option is to return your visa and add your spouse to your application now. If you return the visa and add your spouse, then your spouse will have to pass the medical and background/security checks before a new visa will be issued to both of you. So there's always some small chance of refusal based on these checks.
If you don't want to return your visa, then you'll have to land while still single, marry later (after landing) and then sponsor your spouse afterwards (note that you will have to be living in Canada for the entire time while the sponsorship application is being processed).
What you do is your choice. None of us can make that decision for you.