Ok, obviously not being part of a failed and moribund experiment to create a giant European Superstate is the biggest benefit. A European superstate which is wasteful (they spend nearly £200 million every year on moving the whole shebang from Brussels to Strasbourg for one week every month, then back again), protectionist, restrictive, doesn't produce anything yet bleeds it's member states dry and has bankrupted several - including Greece, Spain, Italy and Ireland. Not being dictated to by unelected bureaucrats who we can't get rid of HAS to be a good thing doesn't it? As does NOT having a bankrupt nation.
It will mean that the UK is free to do trade deals with other nations. This in turn will reduce food and clothing (among other things) prices as, anything imported under a trade deal won't be subject to EU tariffs.
Also, as VAT was introduced to pay for the UK's EU membership, they could, theoretically, get rid of it and make goods cheaper for everyone, they won't though. They could and should then invest the VAT money into the NHS, roads, infrastructure projects and more. Having more money available to invest in the UK, and being able to choose where it is spent can also only be a good things (The EU takes money from the UK, give and gives us back less than half, certainly no more - various sources I have read tell me that for every pound we send the EU, we get between 33p and 50p back. So we don't more than half of what we give them).
Perhaps people like being in an exact replica of the other failed attempt to create a giant superstate, the USSR. I know I don't, along with the majority of people in this country. The EU will have collapsed within five years - it is pretty much bankrupt now (one quote I heard was "If it was a business, it would have closed within three years"). These constructs last about 65-70 years - the USSR existed for 69 years. The EU is heading for that, if you assume it was formed as the EEC with the Treaty of Rome in 1957. I make that 63 years this year.
There is no benefit or sensible argument for being in the EU at all. I have yet to EVER hear one, and I am amazed that any sane or sensible could ever think it was a good idea. It's imminent demise cannot happen soon enough.
Brexit is a massive opportunity for the UK. The EU are scared witless that the UK will make a success of it, and want to make it as difficult as they can for us.