The iPhone 5's speakers are more powerful than those in previous models, so audio is much louder for movies and music. But for some reason, alert sounds (such as for text messages) on the iPhone 5 are harder to hear than on an iPhone 4 in a noisy store, restaurant, or bus. I often couldn't hear them at all, though I could hear the calling tone, which was louder even when using the same ringtone as the other alerts. The iPhone 4 didn't have this volume difference, and I could hear its tones in the same places I couldn't hear the iPhone 5's. The Galaxy S III's speakers are as loud as the iPhone 5's, but its sound is tinnier and less rich than the iPhone 5's (or iPhone 4's).
Some people have complained that the iPhone 5's anodized aluminum back and edges are easily scratched or scuffed. I didn't find that to be true, nor did several other people I know who bought the new smartphone. It's possible that some iPhone 5s didn't cure correctly after the finish was applied. I prefer the feel of the previous iPhones' glass backs, which warm nicely to the touch. The new aluminum back gets very warm when you're using one of the radios and after you charge it -- similar to how the third-gen iPad heats up more than the iPad 2 -- but not annoyingly so. It also gets cold easily. The glass-backed iPhones had less temperature variation. The Galaxy S III's plastic case (available in slate blue or white, as well as in dark red at AT&T only) is pleasant enough, though not as nice as either the old iPhone's glass or the new iPhone's aluminum.
The most meaningful hardware change is the support for LTE 4G cellular networks. Much of the world is only now starting to deploy LTE, so most people will get no immediate benefit from this technology. But you will notice faster downloads and application updates (such as in the browser or in news apps) where it's available -- usually. The speed can be two to three times that of 3G networks in well-served areas.
I've complained before that when I got the LTE-equipped third-gen iPad this spring that I rarely noticed a speed advantage compared to my previous iPad 2 or my iPhone 4 -- at least not in the San Francisco area where I work and live. People in other parts of the country have noticed a real difference. But when the iPhone 5 debuted in late September, I did see faster LTE performance in San Francisco from my carrier, Verizon Wireless, which like AT&T and Sprint has been rolling out LTE in many markets. It appears Verizon has also been reworking slow LTE in places like San Francisco. But LTE coverage is still spotty, and even 3G service is not universal here.
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