Bear: not based on benefits exactly. I'd probably have wanted to remain in the EU if it were in its pre-Maastricht form, and would almost certainly have voted to join in the 70s (had I been around to vote).
Even as recently as a few months before the vote, I was certain I'd vote remain, but considered it such a significant choice for the country, that I spent one or two hundred hours (yes, really!), looking into it in detail. And I don't mean reading campaign literature, I mean reading academic research and treaties, and the like.
I'm starting work in a few minutes, so don't have long, but very briefly:
Supra-nationalism: it doesn't tend to end well, and it's especially concerning when it's been gradually and almost imperceptibly imposed on a group of nations whose people (on the whole) are in favour of cooperation but still of principally being governed as separate countries. When socially and culturally we function as separate nations, it makes it harder to organize proper political opposition or campaigns across the nations, meaning that power is further distanced from voters. Furthermore, it functions in a way which promotes back-room deals where each country agrees to certain legislation on condition that they get certain other beneficial legislation through, rather than legislation doing what is best for all.
How the EU works: Yes, it's a basically a democracy, in that we vote in MEPs. But it functions in a way where a very small number of people have a huge amount of power. MEPs get to vote for or against decisions, but that's pretty much it. They function as a second house - approving or disapproving legislation rather than truly shaping it. Enormous power in the hands of few people, who are not easily voted out, is dangerous.
The effect of the EU on the poor: CAP is shameful and enormously exacerbates poverty in Africa. In addition, the EU consistently pro big business at the expense of SMEs.
I'd have rather we stayed in, and the EU reformed, but the EU has so far shown no real capacity to reform. I'd have also rather stay in for a few more years to see if it might change direction, but it was clear that this was a once in a generation vote.
I knew that I was likely to be financially worse off (and inconvenienced) because of leaving, but put a great deal of effort into determining what I considered to be the right way to vote - the wisest move for the country long-term, even if that was at some economic expense or entailed some suffering for a decade, for the sake of future generations.
I know many disagree with me, and I respect their decisions. But I get irritated by suggestions that because I voted leave I must be badly educated (I have PG qualifications from a top university), ill-informed (by the time of the vote I knew more about the EU and its workings than almost anyone else I knew, a couple of lawyers and and MEP aside), racist (I do voluntary work with immigrants, for a start!), or voting based on feelings (I did more research into this than, I think, anyone else I know).
None of these things proves I voted the best way of course, and I realize there were also good arguments for staying. I also realize, Bear, that you made none of those accusations, by the way!