The first M16s had chromed carriers, but they caused problems with the chrome flaking off and wearing the upper receivers. The Army pulled all of the chrome carriers and declared that rifles with chrome carriers are not deployable (this is still in force, BTW).
If you DO decide to go with a chrome carrier, the ONLY one I would consider is the one MSTN sells. But, personally, I wouldn't spend that much money on a cosmetic item...
-Troy