Well I've been in Forest Hill for the past 7 years and am very happy with it - we are east of the railway in the 'triangle' area between Stanstead Road, Perry Vale and Perry Hill. Its a great area with loads of families and I couldn't wish for better neighbours. My children are at Kilmorie which I am extremely happy with.
From here its easy to walk to either Honor Oak or Forest Hill depending on which shops/cafes I want to go to. I sometimes pop down to Sydenham too which also has a good high street with some great ethnic food shops.
I have a Tesco metro just 5 minutes away so very handy if I don't want to go to a big supermarket. There's a community cafe on Northwood Road, a childrens centre at Kilmorie, St George's church is very active in the community (and also has a little cafe).
Transport - we also have the choice of Catford train station just 15 mins walk away which is on a different line to Forest Hill and Honor Oak, so gives us more choice of transport links. Buses - choice of either Stanstead Road or Catford Hill so lots of options there too.
Park wise we can walk to either Blythe Hill or Mayow Park which are both great - or jump in the car to Ladywell Fields or the Horniman or Dulwich.
We almost bought in Honor Oak originally, but when the sale fell through we found a bigger property in Forest Hill and we have been really happy with our decision. There are loads of good family size houses round here with decent gardens and plenty of parking. I know that people like living near the 'villagey' feel of Honor Oak and can completely understand that, it is lovely, however I think you do pay for it as property there is more expensive than where we are (e.g. we ended up with an extra bedroom for the same price). As with everything just depends on what your priorities are.
However I have lots of friends in Honor Oak too and its such a short walk away that I have never felt much of a distinction between the areas to be honest. Whichever you choose I am sure you'll be happy with it!