The Big Stuff - Operating Systems & Processors
If you're new to the world of smartphones then the operating system and the processor that powers your phone might not seem that important to you right now, but this is really the big stuff -- the stuff that goes on inside your phone that makes it perform the way it does.
There are continuing and endless debates about whether the iOS that the iPhone uses is better than the Google Android operating system that many phones, including the Galaxy S2 use and we've covered this extensively on Bright Hub already. It's totally personal preference. Apple's iOS5 is easy to use but doesn't offer much in terms of customization, Android is perhaps a bit trickier to get started with but is pretty easy to use (even for a novice) and you have much more control about how your home screens look for example. With the Galaxy S2 you get Samsung's own TouchWiz user interface on top of Android which gives you some more areas to play with, such as customizing the size of widgets and photoframes on your home screen using a simple grid system.
The iOS 5 in iPhones also comes complete with Siri which is a major selling point, although in fairness I should point out that you can find very similar stuff in the Android Market to install onto a Galaxy S2 and indeed there is already the option on the S2 to utilize Vlingo (voice powered virtual assistant) anyway. Voice recognition software is nothing that new, although I agree that Siri is very slick and once you have her in your pocket you'll probably wonder what you did without her.
The Samsung Galaxy S2 has a super speedy dual-core processor as does the iPhone 4S, so both will be able to handle tasks you throw at them particularly quickly -- the loading of web pages and the speed of games is noticeably quicker on both these phones than on most other devices. In tests the S2 (along with a few other dual-core phones) was a smidgen faster than the 4S, but absolutely nothing noticeable.