The arguement that a billet upper is better( because it is thicker) could be a bit misleading. First of all, it is thicker because it costs money and time to machine it down to the same profile as a raw forging. That bulk is not needed. A proper light weight upper made of 7075 forging has been in service for over 45 years.
So you are carrying more weight because the manufacturing wants to cut down its machine time - the same thing that AR manufacturers were preaching heavy barrels in the old days because it cost time and money to profile barrels.
I could accept billet uppers are the choices if people want distinctive " custom look" for their uppers, or mono-lithic uppers where there are not commonly available dies to make raw forging. There is nothing wrong with getting something with distinctive asethetics at all. And billet uppers generally have better "fit and finish" because the manufacturers start with a blank plate, not a rough forging shaped by a die. On the other hand, with the availiability of raw forgings, billet upper is the path of " increased resistence" if function and efficiency are the priorities.
We do have to accept that firearms market is like any consumer items market. Sometimes it is all about product differentiation.