They're both amazing arena heroes. Both can be used in raids too, but are not top 5 picks for raids.
So either one is a must have and doesn't make a difference if I decide to get Orkon or Vulko? I was wondering because I will try to improve one of them to 5 stars or maybe make both 4 stars I wasn't sure what to do...
Well they are very different heroes... They are both amazing in arena but do different things, so it might depend on what role you need, or want, the most. Vulko is very squishy but goes invisible at the beggining of the battle, he can kill entire teams by himself but will die in seconds if he is hit. Orkon is very tanky (maybe a bit less with 3*) and regenerates health fast after awakened, he will not deal much damage by himself unless the fight drags on for too long, which can happen since he can stall matches, his ult with make the opponent team attack one of their team mates for a good period of time which can completely screw up certain formations.