I would go Brave-bird over Sky-drop. U-turn is better than Rock-smash. To answer your question, it depends on each move, For Rock-smash it would be 52 Base power with Sheer force, and when you add Life-orb it becomes 67.6 still not very good. Rock-slide becomes 97.5 with Sheer-force and when you add Life-orb it goes up to 126.75 which is great. Hone-claws will boost your attack by 50% each turn so just multiply the moves by 1.5.