iPhone 4S = Apple iPhone 4S
Galaxy S III = Samsung Galaxy S III
Galaxy S II = Samsung Galaxy S II
iPhone 4 = Apple iPhone 4
The iPhone 4S is faster than the Galaxy S III when doing OpenGL graphics as in GLBenchmark 2.1, but slower when running a CPU intensive tests like Sunspider and Linpack.
CROSS PLATFORM APPS
A growing number of apps look and feel and function identically on both iOS and Android smart phones. Some 'matching' games include Real Racing, X-Plane, Minecraft, Angry Birds, Temple Run, Frogger, and Bomb the Zombies. Some "regular" apps they have in common include Pandora, Shazam, Flipboard, CarBuzz, SportsTap, Bump, and Bic Lighter.
The Galaxy S III distinctives include 4G LTE support, a memory card slot, and a removable battery. The iPhone 4S's Retina display has a higher pixel density -- 326 pixels per inch (ppi) compared to the Galaxy S III's 306 ppi. (See features of both side by side on PhoneScoop.)
The Galaxy S III's 4.8 inch (diagonal) screen seems huge next to the iPhone 4S's 3.5 inch screen as you can see from the photo at the top of this article. Having used the iPhone 4S for many months, the Galaxy S III feels big in my hand (almost a half inch wider, almost an inch taller). However it is slightly lighter and slightly thinner than the iPhone 4S. (See specs of both side by side on PhoneScoop.)
We ran 74 download tests in various places throughout our city. Using the Verizon 4G LTE cellular data network, the download speed of the Galaxy S III topped out at 6Mbps. The upload speed topped out at 4Mbps. Using the AT&T HSPA+ cellular data network, the iPhone 4S download speeds topped out at 6Mbps while the upload speeds topped out at 3Mbps.
We took along the Verizon Jetpack 4G LTE Mobile Hotspot SCH–LC11 during those tests. When we put the Galaxy in WiFi mode and connected it to the 'Jetpack,' it attained download speeds as high as 15Mbps. The iPhone 4S attained the same download speeds when connected to the 'Jetpack.'
Lastly, when we put the Galaxy S III into hotspot mode, the best download speed we saw was 3Mbps. So why does the 4G LTE 'Jetpack' download faster than the 4G LTE Galaxy S III? I don't know. You may have seen the tests we ran on the iPad with 4G LTE back in March where it averaged 22Mbps. I guess not all 4G LTE devices are created equal.
If you are a fan of the Android OS, you will be pleased with the Galaxy S III. If you are a fan of iOS, then the iPhone 4S is a great choice. Of the two, I prefer the iPhone 4S overwhelmingly -- but then you could accuse me of drinking Apple "KoolAid."
Some iPhone users may be wishing for a bigger screen and/or 4G LTE support. That wish may be granted soon if the rumors surrounding the iPhone 5 all come true. It will be interesting to see what kind of download speeds will be generated on an iPhone with 4G LTE.
If you are happy with your iPhone 4S but want 4G LTE speed, you could always get a portable 4G LTE hotspot like the Verizon Jetpack LTE Mobile Hotspot we use. When we are on the road, it supports the iPhone 4S, the 2012 iPad (WiFi only), and two Apple laptops. (It provides 4G LTE data connection for up to 5 devices.)