Hi there,
We haven't visited Crystal Palace site, so I can't make a comparison, but I would highly recommend the Abbey Wood site. The surrounding area is nothing to write home about, but the site is an absolute haven, very pretty, peaceful and full of squirrels when we were there last April. The site managers were very friendly and helpful and it is perfect for visiting the city centre, as it is a 5 minute max. walk to the train station. It's around a 20 minute journey to the centre so ideal for visiting the sights. We really enjoyed our stay there and will definitely return. Have a great break!
Karen