With the latest arrival of the Samsung Galaxy SIII, the smartphone race just got intense. Anyhow, if you are wondering what to buy, but cannot decide, or just want to know which side wins, this should help you.
Display
Samsung made it clear that they want to have a huge screen. Some may argue that it's too big at 4.8 inches. Anyhow, the Iphone looks like a dwarf next to the SIII at just 3.5 inches. Although the iphone does have a slight victory in pixel density.
Camera
Both phones draw when it comes to camera power. Both have an 8MP camera with Flash, autofocus etc. And both also have front facing cameras too.
Operating System
Well this depends on your preferences. The Iphone runs iOS 5 while the SIII runs Android Ice Cream Sandwich. (You can upgrade it to Jelly Bean)
Sensors
Both contain Accelerometer, GPS, gyro, proximity, compass. But the SIII also has a barometer. Not sure how useful that'll be.
Battery
The battery on the Samsung Galaxy SIII at 590hrs of talk time is much more endurable than the iPhone's at 200hrs talk time.
Voice Recognition
This is an interesting one. With the SIII being equipped with Google's brand new S - Voice. Youtube videos show that S - Voice is slightly better than Siri. Siri cannot search maps outside the US. Although, different accents may make a difference.
Price
Somewhat surprisingly, the iPhone 4S is still priced much higher at $799 compared to Samsung Galaxy III's $599.

Comments
Detailed comparison. Very useful.