252SpAtk Choice Specs Tornadus Therian (Neutral) Hurricane vs 252HP/120SpDef Flash Fire Ninetales (Neutral): 66% - 78% (232 - 274 HP). Guaranteed 2HKO.
252SpAtk Choice Specs Tornadus Therian (Neutral) Hurricane vs 252HP/0SpDef Flash Fire Ninetales (Neutral): 74% - 88% (262 - 309 HP). Guaranteed 2HKO.
An almost guaranteed KO after Stealth Rock compared to a good chance to live is a pretty good suggestion in my opinion. Especially since he lacks a good counter and you still tank Bullet Punches, a Superpower, etc. decently.
This further illustrates my point. If you switch into Hurricane, you're only doing it once. If rocks are up, in that scenario, you are effectively dead and Tornadus can set up Rain Dance right in front of you to reverse your momentum. Tornadus requires a good check that isn't Ninetales.