I *LOVE* this fan-war of Lucario and Zoroark. Better than Lucario VS Mewtwo (That war was terrible). I support Lucario. Here's why:
Lucario:
1. As a Fighting/Steel type, Lucario has resistances to most moves, including the most used status condition, Poison.
2. He can withstand Sandstorm and have guard against Stealth Rock
3. He has 4 base stats that go higher than Zoroark's base stats, which is HP, Attack, Defense, and Sp. Defense.
4. People argue that Zoroark with Focus Sash can destroy Lucario. However, Lucario can learn the move Bone Rush, which is now outstanding with the new move, Hone Claws. Zoroark kills it with Flamethrower, and i'm pretty sure it's faster than lucario.
5. With Extremespeed, he can outclass a Zoroark's speed gain (So long as it doesn't know Sucker Punch, which only hits if the opponent attacks.).
6. Let's not also forget that Aura Sphere, Lucario's special move, is classed as the most powerful special attack fighting-type move. Night Daze is only impressive with lowering Accuracy, which doesn't phase Hone Claw-based Lucario, along with Aura Sphere.
7. Zoroark's weakness is Fighting, which is the huge boost for Lucario. Lucario is weak to fighting too. and ground, 2 of the most used types in the metagame.
8. Lucario can work in a double battle, learning Heal Pulse and Quick Guard. Zoroark can't compare.
9. His ability is actually useful and not JUST attractive. Illusion can be discovered by entrance if sandstorm or hail is out. Same with Spikes and Toxic Spikes. passive and residual damage doesn't break illusion.
10. Lucario can learn combos with Sandstorn, which is hard for most Pokemon. what does this even mean?
Lucario has, and will always be, my main Pokemon. Zoroark was driven on fanbase to rival Lucario. Although Zoroark has his step-ups towards Lucario, he cannot provide enough combo material.
(But Victini beats both of them, so... yeah.)