I pay the extra bucks for European Sensodyne because it has Novamin in it.

Novamin is like magic, and there is no reason it should have been taken off the shelves in the US (I suspect it's heavy lobbying by the American Dental Association and the Teeth Fae People). Novamin binds and helps remineralize your teeth, very helpful for sensitivity and in conjuction with fluoride can get into the subsurface and helps actually repair the teeth.

Yeah, there's definitely exceptions for people with special requirements. Toothpastes for sensitive teeth contain ingredients like potassium nitrate that wouldn't be in the generic, store-branded ones.