Fly into Kelowna trust me. 2hrs vs 4.5hrs driving, high chance of Eagle Pass being open but Rogers Pass & Kicking Horse Pass are very iffy like Snurf said.
Where are you flying from?
When you factor in the extra transfer cost, the extra time (+ meals, etc), and the possibliity of being delayed hours or DAYS... then it could turn out to be much more to go the Calgary route.
And another bonus... you get to go to sweet Kelowna instead of shitty Calgary
-- Edit --
Definitely a better chance of good highway conditions in March though, vs January-February... but still.