Of the other "Magnificent Seven":
Brompton - highly recommended, very well-kept, several celebrities and artistically interesting tombs.
Kensal Green - interesting but very large and tiring to walk round.
West Norwood - less interesting than some, but artistically impressive Greek Orthodox section
Nunhead - very overgrown, impossible to explore off the paths and hard to see many of the tombs. Good viewpoints of London as it's on a hilltop
Abney Park - overgrown and atmospheric
Tower Hamlets - somewhat overgrown, lacking in well-known people. In a somewhat questionable area where I would recommend obvious tourists NOT to wander alone.