Quoted:
The only reason to use a billet receiver (upper or lower) is aesthetics. If you put form ahead of function, go for it.
Forging creates a superior finished product when it comes to receivers. Anytime you compare a billet receiver to a forged receiver, the billet receiver will either be heavier or weaker (and maybe both).
Ok. That's where I was confused. I understood billet = more weight. I was thinking that there may be some sort of requirement for the extra mass due to the caliber being larger than 5.56/.223, and potential chamber pressure differences. (more powder in the cartridge, depending on the particular load.)
I think I'll spend the $$ differences on aspects that will have a better ROI.
The piece of paper/bad guy/varmint the rifle is pointed at won't care about the aesthetics.