You got it man. Closer to freezing = larger quantity of snowfall (when the amount of precipitation in the air is the same). Of course there's the quality thing too... and man, when you get a good dump on the backside of Louis, it's hard to beat that anywhere!
I've had probably 3 great powder days this year...
Dec 18th at Nakiska. Was heading to Lake Louise but the roads were so bad I barely made it to the Highway 40 (Nakiska) turn off. I convinced my GF we should at least head down for a few runs. We get there an there was 6" of snow in the lot (and most people couldn't make it up the drive into the resort), and I head up top to find a foot of untouched powder. I ran a few laps on some of the steeper runs they have up top, and it was amazing, full on high speed wide carving in the powder! Spent a bit of time in the glades too and had a blast, GF loved the glades.
Mid Jan in Fernie. Went down for the weekend. Saturday was rain/snow, very heavy, very tiring, but fun nonetheless. Sunday they bombed the shit out of the bowls, and I ended up in pretty much bottomless powder in the Cedar bowl for a couple runs, then went over to the other side to try polar peak (which was closed) but I ended up in lots of untouched powder again.
Three weeks ago in Lake Louise. Stayed with some friends in banff, went up to the lake on a wednesday. Got in the parking lot at 9:00 on the dot so got a great spot. Headed up the gondola and found upwards of a foot of powder. Rode down to the top of the world 6 pack, did a few laps, then headed for the back side off top of the world. The powder in the back bowl was amazing! Nice steep fall lines and I hit some natural jumps near the bottom of the steep part, then the long traverse back to the slow lifts.
Out of those three days, I have to say the Fernie runs were the longest, but there were also crowds waiting for the bowls to open, so I wasn't in untouched powder. The lake louise stuff was nice and steep, and relatively untouched, but too short. I almost think the nakiska day was one of the best! The steep runs there have a good enough pitch to really fly on a powder day, but not nearly as steep as lake louise, nobody was on the hill, and there's not much flat area at the bottom to tir you out before hopping back on a high speed quad.
Put it this way, if I had to pick only one resort to go to, ever again, I have no idea what I'd pick. The lake is great in late december early jan because of the amount of sun it gets... Fernie has acres and acres of off-piste riding... Nakiska is close and dependable, it's like the Camry of ski hills, no one really gets excited but it's always there and always works.
I wasn't thrilled with Sunshine or Kimberley. Have yet to check out castle, KH or Revelstoke but excited to try all three.