Like another poster said, it depends on the application. Just on my ARs I have many different types of handguards including lengths and materials.
I tend to like the plastic handguards on the retro replicas best, just because those guns are light overall.
I don't necessarily think they are the best performing. From a few experiments I have done over the years I think free float systems lend themselves better to accuracy, but I am not looking for that kind of accuracy unless I am shooting at something small like prairie poodles. That's among the reasons my varmint AR has a free float aluminum handguard and heavy barrel.
Like another poster above said, I prefer wood on AKs, but I think in that case it is mostly because I am a traditionalist.