Ears, most definitely.
They're just way more sensitive than a tail.
I know because whenever I pet my cats, they have a much stronger reaction to messing with their ears than with their tails.

I hate you, Tamamo.
You were the progenitor of the fluffy weak spots.

Revealing Man's greatest weakness to the world.

Every Man loves cute and adorable shit deep inside, and they can't resist the dark temptation of fluffiness.