You can't compare either of them to UK parks - we did one year going round all the UK ones and it was miserable, expensive, and dull.
Efteling is great - although I can't get my head round the layout despite having gone quite a few times. Food is pretty bad (esp for vegetarians) but it's all so clean and well thought out. The price of the merchandise is amazingly low for that sort of place too. I think you can get cheaper tickets if you buy them in the supermarkets in Holland.
Love Parc Asterix too - food much better there, easy to work out the layout of the place, has a really nice feel.
I'm not a theme park person in that I don't really go on rides, but I have spent so many holidays in them all - so, in terms of rides, my kids have been going since they were babies and some are now late teenagers, and they all love Efteling, Parc Asterix and DLP, but, for me, as non-rollercoaster person, there is still plenty do at them all.