Check out this mortgage calculator: http://www.canadamortgage.com/calculators/amortization.cgi

I put in an example of a 1,000,000 mortgage and left the default 3.7% mortgage rate and 25 year amortization. I selected weekly payments and it told me I would pay $1,175 per week for a total interest payment of $527,860 (see the field called Interest - Amortization.)

I then selected biweekly payments and it told me I would pay $2,351 every two weeks for a total interest payment of $528,394.

So yes, you pay *marginally* more in the second case.: $534 over the life of the mortgage. The economics of that can roughly be understood as the interest you would have to pay over 25 years on a loan of half the difference, since on average you will be running a principal balance in the second case which is higher by about half a weekly mortgage payment. So the difference is very close to $1,175/2*.037*25=$543. Not exact but it gives you a general sense of where the difference is coming from.