Looking for frontside/variable terrain performance,
At your size my first instinct is to say 177. However, it kind of depends on where and how you ski. If you are skiing smaller mountains and like a lot of short turns, I'd go with the 170 and its 13.6m radius. The 177, with a 14.8m radius, would be more suited to a little longer turns on bigger mountain. Not a huge difference, but the 170 will probably feel more nimble.