Plastic, under the assumption it's something super high quality like the Nokia N9 or the iPhone 5C and not cheap plastic like old Samsungs. Durable, feels good, zero radio interference, cheap, easier to work with.
Glass is nice and pretty and you can do some cool stuff with it so I consider it acceptable but I hate that it's standard. Glass is heavy, Glass is fragile, glass is expensive.
Metal on a phone is the dumbest thing. It's heavier than glass, generally more expensive and it blocks signal forcing greater engineering costs to design around it.
ncG1vNJzZmivp6x7sbTOp5yaqpWjrm%2BvzqZmnaGjmMK0v8iopaxndJqvosDEZnmeq6Rivam7zZ5kppmkmr%2BqrctmZGaonJbAtbXCZq2sZl2isrWty2atrGZdnLmiv9KYoJ1pZGyCdX4%3D