There is absolutely a big difference in regards to Canadian vs. US mortgage comparison. Our mortgage rates (here in Canada) are normally for 1-5 year terms, which afterwards are then renewed into another 1-5 year term with a brand new interest rate dependent on the future rate environment. We are not guaranteed any rate at renewal time, and therefore are susceptible to rate increases - especially the longer the amortization on the mortgage. Not to mention, it sure doesn't help that our mortgage interest is not tax-deductible.
The circumstances surrounding your mortgage are most important, just as individual risk tolerances and time horizons are so important in your investment decisions, they are also relevant with your mortgage.
Specific considerations include:
-What tax bracket are you in, and what is your available RRSP contribution room?
-How much longer do you have on your mortgage amortization?
-Your mortgage rate is essentially a guaranteed ROI; are you comfortable with the fact that your investment ROI is not guaranteed? (I.e. market may not perform above your mortgage rate in the specific period you have chosen to invest).
-How secure is your future? From a cash flow perspective, having no mortgage can be very relieving vs. early withdrawing from your retirement account and being fully taxed on the withdrawals.
-What are your mortgage prepayment privileges? Most Canadian mortgages have strict limitations on the prepayments you can make, just as registered accounts have limitations on contributions you can make.
All in all, it really comes down to your individual situation and is very hard to make the mortgage vs. invest dilemma so black and white.
One solution I have found that many clients enjoy is paying off the mortgage aggressively, which corresponding increases HELOC room availability which can then be invested in a Non-Registered portfolio with tax-deductible interest. Should rates increase, they have the option to convert their HELOC into a mortgage component of 1-5 years.