Steelix has an incredible defense, and 4 weaknesses, but with his high defense, he can even take a few super effective hits (from physicals at least) Scizor only has one weakness (4 X weakness)-fire. Scizor also has good physical attack and defense. And both have access to pretty powerful moves. Steelix if you need a wall that can hit fairly hard, scizor if you want an offensive pokemon with one weakness.