for all intents and purposes of the current metagame, crunch is the superior option. a lot of teams right now carry 2-3 ground immunities since eaerthquake is so common and crunch takes care of ghosts that switch in on CC. it is the superior choice
Honestly tho, Earthquake has it's advantages to. It deals with (most) Fire types and Ground types who Lucario is weak to, while Crunch doesn't do SE damage to them. It depends really. If you are not running a ground type, Earthquake is especially handy to. Plus things that avoid EQ shouldn't really switch in on Luke at the risk of Lucario setting up (I would think?))