Haxorus one million percent. Why? Availability. Axew is available around mistralton city, if I'm not mistaken. That's just halfway into the game so it's not too unreasonable. What is unreasonable is Hydreigon. You can't catch Deino in the wild but you do get Zweillous but it only becomes available at the victory road, which is super late, and it is available at level forty nine and fifty. It gets worse as Zweillous evolves into Hydreigon at level sixty four, which means that you would have to grind your ass just to evolve it
This makes Haxorus the superior choice. All you need to do is nag an Axew in mistralton cave, level it up and teach it brick break. Throughout the game, it's arguably the strongest in game mon as the only moves it needs are dragon dance, dragon claw and brick break. Two of the moves are available by level up while brick break is a tm you get in I believe driftveil. Aside from that, Haxorus also has an incredible ability that makes gen five so much easier, mold breaker, because this game is infested with the most annoying ability an npc could get their claws on, sturdy
