Hi guys~ i just wana get opinions before purchasing an iphone~

If i buy a overseas set~ means i need to jb and unlock it~ i cant update it rite?? does it make me to have lots of disadvantages? coz i heard from my fren that the updates are important~ no updates = useless.. is that true?
i can still use like normal rite?
still deciding on digi set or overseas(US) set~ but digi is expensive~
hope you guys can tell me and please dont flame my noob question~
thanks for reading~