The drive can by iffy anytime in the winter. As you may know, Revy is subject to a particular avalanche risk on both sides (Three Valley Gap on the west, Rogers Pass on the east) so if there is a big dump you may face considerable delays. Having said that, they are having a great season so the riding should be great in March. I'm probably heading there next week.
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.
I agree Kelowna is a better choice if Revy is your destination. The only advantage of Calgary would be that you could get a day or two at Kicking Horse on the way to or from Revy. It doesn't get the snow that Revelstoke does but is a pretty awesome mountain in its own right.