It sucks to bend a pole in the middle of a great day; go composite, carbon fiberglass types. I once had mine leaning against the back of the car when I pulled out of the spot. car wouldn't go. I got out and looked behind. the poles were wedged and the car wasn't moving. they're strong enough. Steeper terrain with deep snow = slightly longer pole, otherwise the formulas are fine.
Until they snap when you make a plant and they impale you (I've seen it ALMOST happen). My friend Jack can vouch for my statement:
Either go all aluminum or go half aluminum and half carbon. I use the latter of the two for everything (aside from DH cuz the Alu-Carbon DH poles are REDICULOUSLY expensive; I use aluminum for DH/SG). Haven't had a problem with my Leki's in the 2 and a half years I have had mine.