Dual Chop
+ Breaks Sash
+Breaks Sturdy
+ Breaks Substitute
- Less Accurate
Dragon Claw
+ Higher Accuracy
- Susceptabl to sash sturdy and Subs.
Personally I would take Dual chop. The ability to break subs and sashes is pretty handy.
But Dragon claw is also good if you want to play it safe. and If Haxorus' ability is Mold Breaker Dragon Claw can still OHKO Sturdy pokes.