Steelix has great defense stat and outclasses Cobalion in that aspect. Contrary to Steelix, Cobalion's stats are nicely devided and not to forget it has a pretty good typing (A legendary Lucario). Cobalion has great defense, decent attack and speed and has a large movepool. Steelix is definitely a good Pokemon but if you are looking for more I would recommend you using Cobalion
