That really would depend on your budget, your season, and what you want on your doorstep.
Biarritz is one of my favourite European cities. It has a slightly faded regency splendour, restaurants with excellent food at every budget (check out the Casino restaurant, accessed from the beachside) and some of the best surf beaches in Europe, in the centre of town and to both north and south.
If you want sea views but not city centre prices, try Bidart - there are a few hotels etc to choose between - which is only a bus ride back to the centre.