The couple years I spent over there I dug and dug for stats and info on snowfall amounts and consistency. St. Anton, Engleberg, and Andermatt win in this regard.
Spent a week in St. Anton every year for the last 4 and have had at least thigh deep every year! The Rodelbahn there is very fun but very dangerous

Search for pictures of my trip from last year.
Oburgurgl is largely flat and while snow sure because of the elevation, doesn't actually recieve that much snowfall. Yes there is good touring, but the verts a little small and there just isn't much steep around there. If you think Zermatt doesn't have anything steep then Oburgurgl definitely doesn't have anything steep.
The town of Andermatt kinda blows. People weren't particularly friendly (wife speaks German so it wasn't an American thing), expensive, food very marginal, and just not fun. Fun medium size mountain with lots of snow. don't be there on a weekend as the crowds from Zurich were a bit rough.
La Grave/Serre Che while having absolutely amazing terrain, really cool glaciated routes, awesome vert, has unreliable snow. Alagna is all that and more inreliable in the snow realm. If you hit it with good snow its fricken insane, but the probabilities when traveling that far aren't in your favor.
I would go with St. Anton or Engleberg. Literally the only thing you miss out on in St. Anton is glaciated terrain with huge vert. Engleberg has that, but probably not quite as fun a village/vibe without the Mooserwirt/Kangaroo, Tirolean vibe.
Verbier is definitely on the dry side and very expensive. good terrain though.
Champery is way too low. Went there 3 times. Once was great, once was raining, and once was green grass. We kept moving East on that final trip. Verbier was hard pack and ice, and Zermatt was soft fluffy 6inches of fresh. But altitute matters in the alps so I wouldn't fly over from the states for Portes du Soleil because you never know if it will rain.
Sounds like good fun. Damn I love the Alps. This will be the first year in the last 5 I won't get over there.

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