I think I might have to go with charizard. I love arcanine because he has much better abilities and higher stats. He has a lot of speed, attack, and sp. attack. But, to me, it's either you make your Pokemon a physical or a special Pokemon - not both. Charizard however majors in sp. attack, plus he has a lot of special moves. Also, charizard has 2 megas, so you can choose what path you want. Arcanine has the same amount of weaknesses as charizard, but charizard can resist a lot of types too. Arcanine learns much less moves than charizard, therefore, he doesn't have much of a wide variety.
This is your decision!
Hope I helped! :)