Oooh,
Probably not W Dulwich as the public transport is far more restricted .
The Herne Hill one for the stroll over the road to Brockwell Park, the Lido, the very easy access to a great range of neighbourhood shops and bars, and the two good rail connections from H Hill. V quick bus ride or 20 ish min walk to Brixton for tube, cinema etc. Has a bigger garden than Helix Rd, BUT would be noisier. There is usually a short queue on the junction, buses on the main rd. Is that off road parking in front of the house? You'd want that, there, if poss.
Helix Rd: great rd, walking distance to Brixton with it's tube, cinema, shops, fantastic restaurants and bars, theatre in a couple of years. Also walking distance to Brockwell Park . Disadvantages: not end of terrace so no access to back except through house.