I've been to Banff and boarded the big 3, we had a fair bit of snow while we were there but Japan has the best POW record by far.
Niseko in Japan averages at 12m of snow per YEAR! That's an epic proportion but I agree with WasatchMan, it totally depends on what terrain you want to ride and if you can financially afford it!
I'm flying from the UK and it costs me around the same (Japan/Canada) if I book separately and avoid package deals. I'm returning to Banff this February, epic place and I highly recommend it! I've only been boarding since 2011 (had three trips so far, Banff, Les Arcs, Val Thorens) and I still don't think I'm near the right skill level for knee deep POW!