Ummm....I need more info...where do you ski, is it just park, or all-mountain too, what's your ability level, how much rails vs jumps.
At first glance, I'd say 181, but that could change based on above info (if you do TONS of rails and basically no jumps and all-mountain skiing, and/or you're not a very confident skier you may consider the 176, but otherwise, you should probably grab the 181).
Since you're doing more jumps go 181, it will be more stable. But really, it doesn't make much of a difference. It's 5 cm (2 in) you can measure that out with your index and middle finger. You really wouldn't notice it that much.