Basically samsung is korean based telecom company. They made different versions of same mobile models acccording to people's choice and regional demands.
Korean mobile are also original Samsung models but they are specifically made for Korean region. Like they have antenna in their mobiles so that they can watch online television. Even samsung galaxy S2 has antenna. Now new Korean versions are free from antenna. Korean version of Samsung Galaxy S2 has 2gb Ram. And all the remaining versions has 1 gb Ram.
But if you want to buy Korean version of Samsung mobile then you have to keep in mind 2 things.
1: Korean mobiles operate on some specific frequency. Like i had Smsung Galaxy S2 but i didnt face such frequency problem. But if you see that your mobile is not operating properly then you have to change the frequency according to region. But this problem mostly occur when you want to use 3g and 4g mobile data services. kindly don't do your yourself while changing mobile frequency. Get the services of some expert.
2: if your mobile got damage then it will be difficult to get spare parts of your model because its difficult to find original spare parts like LCD'S, Battery, Software damage problem.
But in short Korean versions are faster, they have a lot of market share because lots of people only use Korean versions.