No one I know cares about HTC, all just buy Samsung now, they make better Smart Phones and the whole metal vs plastic thing, no normal person cares, most people put it in a case anyways. The only person left who is my close friend, got fed up with another bad HTC camera and wants a micro SD so is now buying the GS4.
Personally myself, I'm only sold on the GS4 if it has Exynos with 4G, though I've been using a Nokia lately and I really like it, so I might wait a few months to see if they announce anything, before buying a GS4.
The GS4 just offers everything and tbh plastic is superior to metal for a phone. If it was about conducting electricity or heat, then I'd say yes, use metal lol. Tbh just buy a new back cover if you hate the default one.
Don't get why no one is speaking about the poor mic placement on the HTC One, on the back? Please.. rookie mistake right there.