var, it's not a simple answer, it would depend where I lived.
I don't rate the private schools that are local to us, but the state schools are excellent, so living here, I would obviously choose state.
Where I lived previously, I didn't rate the state schools or the private schools greatly, so we moved to a different part of the country before dd started school. I realise that we were lucky to have that option (and to have been able to buy our way into the catchment of some excellent state schools.)
If I lived in an area with really good private schools and significantly less good state schools, I might well have gone private. Politically, it might not have felt great, but ultimately, I would have chosen the school that was best for dd. My principles are not that strong.
The only type of school that I would never have considered for my dc would be boarding - state or private. While I know that anecdote is not equal to data, there is a far higher prevalence of mental health problems among those of my acquaintance who have boarded, and I would not have been willing to take that risk under any circumstances.
I am certainly not denying that state schools in some parts of the country are pretty poor, and private may well be a better option in those areas. What I take issue with is the assumption that private is inevitably better than state just because you pay for it.
I'm also not denying that some private schools (but very few IMO) offer a wider range of opportunities for children. However, I haven't yet seen or heard of anything of value that a clued-up parent couldn't replicate outside school at a fraction of the cost. Not single-handedly, of course, but using the funds that we save on school fees and our existing networks - surprisingly I have one, despite going to a comprehensive school! 