There are many valid points here.
Statistically most mortgages don't last for 5 years. You may lose partners, you may decide to sell, or you may have equity that you and your partners would like to pull out with a refinance. It is quite understandable to choose the fixed rate for peace of mind, especially considering the rates are at historical lows. And if you choose a 3-year term, the rate will be even lower (by as much as 1/2%).
Variable is a great option to maximize cashflow while prime is so low, but only if it fits within the expectations and risk tolerances of all parties involved.
With some institutions, you can put fixed or variable mortgages (or a combination of the two) within a "Total Equity" product that allows you to pull out equity with a HELOC set by today's property value. Very helpful for major reno's on the property or to payout partners, and no refinance involved. With a $250k property, you may be approved for a $200k mortgage. Your HELOC can be set to automatically increase as you pay down the mortgage, leaving you with $200k total available credit.
I also agree that your quoted rates for variable and fixed seem quite high.