I wouldnt choose Camps Bay (it would also be my last choice without looking at the prices factor). Camps Bay is lovely and the beach is beautiful, but it is much more convenient to stay in town and do a day trip to Camps Bay, than to stay in Camps Bay and having to drive into town for most attractions.
De Waterkant is great, as its in easy walking distance of the V&A and plenty of attractions in central Cape Town. It has a pleasant atmosphere and many restaurants in the immediate area. Also, depending on where you stay (and how high up, you can have great views).
Sea Point is pretty strechted out, so it might depend a bit where you are looking to stay at. Generally said, its also a pleasant area to stay at, and there is good choice of restaurants. Some streets can be a bit dodgy at night.
To make the choice even more difficult, I will add another location :-): Gardens (including Tamboerskloof and Oranjezicht), this is my favourite area to stay at in Cape Town. Plenty of lovely and quiet residential streets, safe to walk around, plenty of restaurants and bars, and the city centre and V&A in walking distance.
