Whatever feels more comfortable to you. I ride +15 / + 12 most days, +12 / + 6 on a deep pow day. You should not carve in pow..as soon as your edge bitres it you will slow down too much...glide-turn over it and keep you nose up.
Groomers are for fast edge carves...
2012/13 -12- Kirkwood days
Arbor A-Frame 158 2009-10
Jeremy Jones Hovercraft 156, 2011/12
Subaru WRX 06