I disagree with a few people's previous assessments of the festival. It really depends what you mean when you say 'overall experience'.
Benicassim (similar to, say, Reading & Leeds) as a festival is simply an arena with a few stages built in for you to go and watch gigs. If by 'festival' you mean 'watching gigs' then Beni is perfect for what you're after. They also have the beach, as said.
Because you've said you're after 'the best experience overall rather than lineup' I'm gonna take that to mean you like experiencing everything festivals have to offer, the 'mini-city environment' if you like. Like Glasto, Bestival or Boomtown. I'm going to Sziget for the first time this year so I can't offer you loads in the way of knowledge about it but if you take a look at how it's laid out and everything that goes on there it sounds a little closer to what you're after imo.
Both options good depending on what you're after, I'm more of a mini-city guy personally. Glastonbury is the only festival in the world which can offer both that and an A-List lineup, which is why it's the best.