First of all, The pronunciations are different. Well I'll tell this focusing on Seoul accent because it's the standard accent of Korea. Seoul accent is kinda monotonous, We usually rise the inflection of voice in conclusion. But in my opinion, North Korean sounds pretty undulate. And also there are so many differences in vocabulary. For examples, We say 가끔(ga-ggm) which means 'sometimes', but North Koreans say 가담가담(gadam gadam) And they say 디대(di-dae) which means 'stair' but we never understand what 디대 means. because we say that 계단(gye dan) in South Korean. And South Korean seldom use words that are from foriegn languages and make new word. for example, we just say 아이스크림(a-ii-s-k-rim = Ice cream) but North Koreans say 얼음보숭이. 얼음 means 'ice' in both of south and north korea, but I don't know what 보숭이 means. And the rules of spelling are different in some same words. we write 연계 but they write 련계, as like you may see on the bottom of this page. (I never understand why that was wroten like that on italki site..It really seems like North Korean word anyway..) I hope It can helps you.

Ah...I just found my mistake.. I mean South Koreans rise the inflection of voice in conclusion WHEN WE ASK A QUESTION.