Milling the sear trip portion of the carrier does not reduce its functional strength. It rides straight back and forth. The trip area of a FA carrier does not increase its functional strength.
The difference in weight between an enhanced, current SA Carrier vs a current FA carrier is measured in grams, whereas the differences in weight between buffers, which move in tandem with the carrier, is in ounces. If someone wants to change the weight of the moving mass of BCG and Buffer, the buffer is the place to look.
It makes no difference to function, performance or bolt life. Sounds cooler to say maybe?
I can never understand how people willingly pay more for a FA BCG because it is FA. If anything, the SA carrier takes another couple seconds to manufacture. I know people who have purchased inferior brands of bolts (when I say inferior, I mean their bolts and bolt hardware break quicker than some other brands), because it came with a FA carrier. Boggles the mind. The carrier is not what breaks. Buy a good unit from a known manufacturer.
Then there are other companies selling lightened carriers, and other people extolling the virtues there.
If someones rifle isn't cycling properly, the difference in weight between a FA and a SA carrier, won't be the cure.
FWIW: We sell both.