I live in Panama and i run a cellphone shop. Here we are unlike the US, people buy their phones unlocked and put their own sim card on it. 80% dont use contracts. I sell all types of galaxy series phones, including high end S2 LTE, Note, Nexus, etc.
My personal phones are iPhone 4 and blackberry 9900.
It is sad but true, after a couple of test, even the blackberry has smoother menu scrolling and any of the galaxy phones. They do lag. You can see this in the lockscreen, menu and when pinch zooming a picture very quickly.
Im not here to troll or bash, just to tell my personal experience with these phones, with emphasis on the lag issue. I believe a good phone is not how good they are at hardware but how they execute the software.
My first computer had 600mhz, 64mb ram, no gpu, ran windows 2000 at 800x600 and it scrolled pretty smooth, I just couldnt stand a decive many times more advance to fail on this, This is why I dont own an android phone.