By all means use glass for the lenses and metal for the heatsinks, but building the entire thing out of metal is harder to justify IMO. I doubt they're heatsink

By all means use glass for the lenses and metal for the heatsinks, but building the entire thing out of metal is harder to justify IMO. I doubt they're heatsinking directly into the case, that would cause it to radiate heat into and around your face rather than being directed away by fans, and make the unit uncomfortable to handle after its been used heavily. The front glass is more scratch resistant than plastic but in exchange it's going to be instantly obliterated if you drop it the wrong way, so pick your poison.