Arcanine Pros:
Great as a mixed attacker
Vast movepool that covers its 3 weaknesses to Ground, Water and Rock
All abilities are great (Intimidate, Flash Fire, Justified)
6 Type Resistances
Can learn ExtremeSpeed and other priority moves
Arcanine Cons:
Outclassed by faster Pokemon
No Mega-Evolution as of yet
Houndoom Pros:
6 Type Resistances
Mega-Evolution
140 Special Attack and 110 Speed with Mega Evolution
Immunity to Psychic Types
Flash Fire/Solar Power
Houndoom Cons:
Loses an item slot due to Houndoomite
4 Weaknesses, and no longer resists fairy
Frail when not Mega Evolved
No priority with sole exception of Sucker Punch
Mostly physical movepool
If I had to choose which one was better, I would choose Arcanine. It's even classified as the Legendary Pokemon!
