What is the difference between the surgeon fish and a tang?

The fish families including the naso, acanthurus, paracanthurus, zebrasoma and more all have a weapon either side of their peduncle and mostly, their individual weapons dictate what is a surgeon or a tang!  

Surgeon fish have a blunt head style like the clown and blue surgeon fishes and are omnivores.
Surgeon fishes weapon, the razor blade like weapon cuts like a surgeons scapple.


Tangs have a pointy face, as an example, like the scopaz and are all herbivoes.  
Tangs weapon, though many have just one spike, this weapon rips the flesh.