Don't get me wrong… Les Arcs is a nice spot and altho closed at the moment (if not, then for most of the time since it opened) the double decker cable car linking it to La Plagne is pretty kewl.
Here is some of that space Joe mentioned:
http://www.snowboardingforum.com/pho...00&ppuser=1645
And some of the steep
http://www.snowboardingforum.com/pho...00&ppuser=1645
But for cool, as in freeze yer bollocks off, I would suggest cervinia.
You can access Zermatt from there (so pack your passport when going up the hill) and it is proper high up….
You can go inside the glacier up on Monte Rosa, enjoy a bit of altitude breathlessness and then of course ride down. All from the lofty height of 15000 feet and with a constant view of the matterhorn
http://www.snowboardingforum.com/pho...00&ppuser=1645
But really if you want a high quality terrain park; mad cliff drops; endless back country; wide open powder fields and natural hits and pipes; or just the highest serviced run (not to mention the highest euro mountain) then it has to be the collective of le tour, argentiere, la flegere, le brevent which make up the the Chamonix Vallee. And then there is the endless night life.
I love italia, switzerland and austria but ultimately Les Phrench win it for me.