A friend asked me "How is samsung galaxy S2? Worth buying?"
In one word I can say Yes, but I being me would go on and on and on.....
SII got a 1.2 GHz dual core processor and 1 gb ram, iPhone 4 has 1 GHz single core processor. I found SII is much faster than the SI and iPhone 4. But watch out for iPhone 5.
Samsung got a 4.3 inch screen bigger than 3.5 inch apple screen. But iPhone has super high resolution retina display compared to Read somewhere that iPhone screen is less power intensive and reproduces colors better but that does not mean a lot as of now.
The Body is plasticky, SII back cover is flimsy, made of slim plastic, seems will break down at any moment. iPhone 4 has a industrial design, it is the sturdiest you can get ever.
The OS in Android 2.3 (ginger bread) is far more stable compared to 2.2 and 2.1, but iOS is most stable any day. Personally like using a Android OS compared to iOS, because of the Home screen and Apps screen separately. Expect iOS 5 to add more features to the stable and then I might have to change my opinion.
Overall i feel iOS gets better apps than Android. Don't like the Android App market experience, most of them look lot less polished than the iOS apps. Most of the apps I use however are available on both platforms so it does not matter.
I like the integration to Gmail/Google Apps/Social Networking in Android. iOS will have integration with twitter in iOS 5, but it is far less integrated.
Battery... I used to run out of the iPhone 3GS in half of the working day with SI somehow get to the end of the day (because I play with SI far less compared to iPhone), with a Blackberry Bold I would use 2 whole days. Displays consume most battery apart from the calls, bigger and touch screens even more.
If mail is the primary use of the phone Blackberry is better (Bold Series (avoid Torch) but look out for the new ones coming. For high apps and games use I would recommend iPhone. SII gives a more balanced user experiences.
Finally; when I bough the SI I though to myself that it is a poor mans iPhone. I still stick to it. SII gives far more value for money spent than iPhone.