Charizard Y can take a hit better than Ninetales. It has 78/78/115 defenses to Ninetales 73/75/100. It has (slightly) better typing, having 6 resistances, with 2 4X resistances and an immunity. It's equally weak to hazards, as Charizard Y is immune to Spikes, Toxic Spikes, and Sticky Web. Literally the only reason to use Ninetales over Charizard Y is for a Heat Rock. Charizard Y even learns Roar, so it can fill the bulky phazer role.5.) If Zard Y ends up in the same tier as Politoed and/or Ninetales, he's going to get major competition from them for a spot on a team, and both of them have better movepools and can actually take a hit (plus Politoed switching in just screws you over).
When you are switching Charizard in, Politoed will need to be extremely weary of switching in, because Charizard can mega-evolve, shut down the rain, and destroy it with SolarBeam. Or if you are predicting your opponent will wait, you can set up with a Flame Charge or Dragon Dance (or any thing else without Mega-evoing)