I have a Samsung Galaxy S2 Plus. It's a good mobile but I think iPhone 4 or 4s is better...I'm trying to change a.s.a.p. my telephone and buy an iPhone. Do you think it's a good choice? What of them is better?
Anyways, just get an S4 or S5 and call it a day. Hell, even the iPhone is better than what you have currently so I wouldn't knock you if you went that route.
If you want a minor upgrade, but want a phone that is fast, runs the latest OS and runs all the apps etc. an iPhone 4s (not 4) is the winner.
If you like your current experience, but want it faster, get a S3 or a new phone.
Don't listen to "iPhone is basic, Samsung is laggy" because it's all bias. Each phone is catered to a different user, and not every person is going to think the same on each phone.
The iPhone is generally more reliable, but the Galaxy has more customisation.