Looking at ING's webpage they show their variable at 5.10 and their fixed at 5.24%. (And I bet hockeymortgagemom, Jessica, could beat that rate since it's their posted rate).
So, if prime rate didn't raise at all during the 5 years or it went down, variable would be the way to go, but with such a tight margin even a .25% increase might make a variable rate mortgage more costly over the 5 year period (you'd have to run amortization schedules and "what if" interest rate hikes to see where the breakeven point would be if you had part of the term at 5.1 and part at 5.35 or higher).
That said, today's decision may also influence your decision...
http://www.bloomberg.com/apps/news?pid= ... fer=canada