I've always said there are two types of people in the world - those who like Nags Head and those who like Myrtle Beach. If you are looking for a quieter vacation (i.e. no amusement parks, no choices of putt-putt, not tons of restaurants, etc.) then Nags Head is your place. Myrtle Beach has A LOT more going on - amusement parks, lots of different putt putts, outlet shopping, restaurants, IMAX theater, places like Medieval Times, Dixie Stampede, etc. (I could also add "traffic" to that list - LOL!!) I do like the beach better at MB - it's flatter, whereas NH has a steeper slope and is more prone to rip tides.
Now, I'm a MB type of gal myself, but I know just as many, if not more, people who love Nags Head and don't like MB. They want a vacation that is quieter and don't want the hustle and bustle of MB.
My favorite place to stay in MB is called the Long Bay Resort. It's between North Myrtle Beach and Myrtle Beach, so it's easy to get from one area to the other. It has a big pool, a covered pool, several hot tubs, and a lazy river. It is also oceanfront.
If you have any more MB-related questions, I can probably help you with those better than I could NH questions, although I'll do my best! I've been to MB about 17 times and Nags Head about 4 times.
Good luck in deciding!