Primrose Hill for me. SJW is nice enough but parts feel like they are trying to be in Buckinghamshire rather than in London, despite the excellent location. Bland sums it up quite nicely. Primrose Hill just feels more London though it lacks the tube station. Hampstead is lovely with some delightful houses but the traffic is a sod (should you be unfortunate enough to have a car). Bits of Maida Vale are pretty nice too.