This thread poster asking about the performance of these 2 phones. Anyway about features there are lot of things in iphone 4s which are better than Galaxy S2 too, like great UI, screen, more refined OS, Camera quality, App store, icloud, etc..
Anyway since you are talking about bang for the buck and usability in Sri lanka, i think both of these phones are over priced tech enthusiasts or showbiz products. You can buy lot cheaper phone with all the essential features of these phones. Who wants a top end cutting edge phone for negligible performance increase in daily use. You may say i need Dual core chip to play games. But other phones also play the same games with a fraction of the cost you pay. You can buy the best VGA card in the world for the difference and fix it to your PC.
When you come to the top end it's not about bang for the buck.