The MacBook shown at left has a polycarbonate plastic exterior, while the MacBook Pro (right) is aluminum. Both materials have their pros and cons, aluminum is stronger so it can be thinner than plastic yielding sleeker notebooks with that "I'm expensive" look. Also, aluminum may provide better cooling for the interior components of the computer than plastic. But when it comes to durability, my personal experience tells me there's no clear winner. Under impact or stress polycarbonate can dent, and aluminum can warp or dent. However, based on my observations, aluminum can be damaged more easily than plastic. Read on for why polycarbonate might just be a better material for laptops.
Most of my friends with PowerBooks (the aluminum predecessor of the MacBook Pro) have dropped them. And while they all seem to still work, the lids don't close properly anymore, the corners are dented, or the exterior is warped. However, I've never seen an iBook (the polycarbonate predecessor of the MacBook) with anything more than light scratches on the exterior. Polycarbonate is a unbreakable plastic, it's used in bullet proof glass and for CDs. If you've ever tried to break a CD the plastic doesn't really snap as you might expect, instead it just creases like really stiff paper. Under extreme impact Polycarbonate can dent, and if you really go ballistic on it, you can break it. But mostly it just yields to the stress and returns to it's original shape. Like polycarobonate, aluminum can dent on impact. But unlike polycarbonate it bends and warps under stress. It's usually some warping that causes laptop lids to not close correctly.
While Polycarbonate seems to do a better job of protecting itself than aluminum, it's hard to know which actually protects the internal components of the laptop better. On impact polycarbonate may flex enough to dislodge the guts of the laptop, over time a warped aluminum laptop might be able to stress and dislodge the components long after the impact.
Dell posted a video showing some pretty extreme stress test on their Latitude D820, which I don't think is even made out of polycarb. I'd love to see some similar tests done on a MacBook Pro. As much as I love the look of aluminum, I'm not sure if I'd prefer looks over durability. Especially since the polycarbonate laptops from Apple are totally hot too.
If anyone has pictures of a damaged iBook, PowerBook, MacBook, or MacBook Pro they'd like to share please leave a comment with a link to the image.