Who needs guarantees?There is no point in contributing to the TFSA..when you have a mortgage.
You are guaranteed to save yourself $$ by doing that.
There is no guarantee that a TFSA investment can do that for you.
When done properly (accounting for risk exposure), leveraged investing can pay off big. Ask anyone who decided to put money into the market between late 2008 until today. Mortgage rates have been abysmally low, so like usual, the guaranteed return from paying down 2-4% mortgage debt has been poor compared to returns from equity markets (upwards to 100's of %).
A one stop 'pay down debt' suggestion is a little limited in my eyes.