Depends on other factors for me. Local state is very good. Local prep is excellent. We have gone for the prep option - DD starts In September. Why?
The state school didn't have the same "feel" as the prep when we visited. We visited several schools (state and primary), narrowed it down to one state or one prep, and then we just got a certain vibe for the one we chose.
Also, it has a better after/before school option for us making our life easier on my work days. With the state school we needed to consider the use of a childminder and they are not easy to find round here.
The head teacher at te one we choose seemed soo much more welcoming that the state head teacher. She knew our names and DD's name as we entered the school and took the time to chat to us.
The state school on visiting did not acknowledge DD hardly at all. They just spoke to us about the school and pretty much forgot DD was there. The prep teachers spoke directly to DD at least as much as they did to us, probably more. They were genuinely interested in her and what she had to say.
DD's prep has a wide mix of children from different cultures/relgions.countries - more than the local state.
There is more emphasis on other, non-academic or enrichment subjects at our prep than the state. DD will do all manner of sports including ballet, she does French from Y1, etc. And there is an extensive after school activity/club list on offer.
We already have a good social thing going on in our local community with DD and she attends a dance school outside of school/nursery too. She is also interested in joining Brownies in the ciommunity when she is 5. Besides many of the children where we live go to other preps and other non-catchment states round here too.
Class size was a big thing too. DD will be in a class of 14, with a FT experienced class teacher AND a FT experienced teaching assistant.
We have gone for single sex. No reason for this, but most of the private schools here are single sex and the only mixed done I wasn't keen on. I don't for one minute think this will affect DD at all as she has friends on both genders outside of school. My mum went to single sex grammar school - she turned out just fine, LOL!
But you know what, still the main over riding factor in my choice was that vibe, that feeling that it was just the right place for DD. I am just so sure that she will be ahppy there and will fit in well. It feels like such a lovely school. And it was tht feeling I went for, and would have always gone with regardless of if the school was state or private. We were just lucky that we had that choice open to us - we had more choice to start with to make our decision from. I hope my "feeling" proves right. Time will tell.