I see you have asked this question on AR15.com, maybe a bunch of other forums.
Makers of lightweight carriers claim that it will increase the cyclical rate. A questionable advantage for a semi auto.
I think a lightweight bolt carrier is a bad idea. A heavy bolt carrier is a positive. For AR’s, reducing dwell, by adding weight to the carrier is a desirable feature for reloaders.
Increasing the mass of the carrier is also desirable as it improves function reliability. The best military rifles have high ratios of “carrier” weight compared with bolt weight. The more mass there is available to strip a round from the magazine and close the bolt, the more reliable the mechanism will be.
The AK47 has a particularly high carrier to bolt weight ratio. I have not weighed my PTR91 bolt group, but it is no coincidence that the mass of the carrier is so high.
The AR has never had the reputation of being as reliable as either of these rifles, adding a lightweight bolt carrier would be a step backwards for this design.
In my opinion.