I never stayed at Mata Chica... but their restaurant is my favorite and I've spoken to many guests there. The north end is definitely more quiet and private for those who want that, and there are enough options now up North for those who don't want to head south into town to have some variety within walking and golf carting distance.
Do check out the topics on this board though to get the pro's and con's. In particular, find out when the last boat back North is and see if this fits your needs.
Bottom line... do your homework... ask all your questions here. What's important to you? Privacy? Restaurants? Location? Side Trips? Noise? Price? Pool? AC? Night life? Amenities? It's hard to go wrong as long as you are specific on your priorities.
Enjoy your anniversary! (What number will this be??)