The politics side
I'm not going to pretend to understand macro economics enough to really debate on whether membership with its fees is better or worse than non-membership and a negotiated trade with the EU (though I am far from convinced by Nigel Farage's basic argument that the UK can trade with commonwealth countries to the same economic success); because if I do, Mankind will send me for an early bath.
The politics side though...I will simply present my POV for what its worth (having dropped the ever-neutral stance I have to take as a politics teacher).
Most people's problem with the EU is something called democratic deficit - this is when there is a part of the system in a democracy where there is no accountability to the public. The EU has it, the House of Lords has it. For both entities it is entirely possible to make a case that the lack of accountability/democracy is better - democracy and good are not the same thing regardless of western rhetoric on such things.
The core of that argument is that there are various forums for the airing of public opinion - any elected chamber such as our House of Commons - where public dissent results in a change of membership to that forum. There can therefore be other forums where public whim is sidelined in an effort to do what is right over what ios popular, or to balance the needs of a minority over the desires of a majority.
The 'better' argument will always revolve around what an undemocratic chamber has done recently and the opinion of the public on such a topic. You will often find public hypocrisy here - perfectly happy when the chamber does something they like, screaming about abuses of power when the chamber does something they do not like.
And herein lies the core of my argument - people complain about democratic deficit, but democracy is a) a myth and b) a stupid idea.
An individual person has a set of beliefs. A people do not - they are simultaneously in favour and against everything. You could solve this by majority rules; but remeber that in gang rape, 9 out of 10 are quite happy (doesn't make it right).
The Stupid idea:
In a democracy, any two idiots can outvote a genius. So you need a state with more geniuses than idiots. Let me know if you ever find such a place.
A simple analogy shows the problem. If you went to hospital would you take a show of hands from all the people in the waiting room about whether to take the prescribed treatment?
Yet, we use such a process for deciding health policy, and education policy, and defence, justice, taxation, welfare, business and economic issues....
So, what's better than democracy? A republic with an elected chamber to oversee government competance (but not actually make policy).
My simple comment on economics:
The problem with the EU is the wealth disparity between nations matched to free roaming which results in influx to wealthier places. Solution - federalise the EU. Every person stops paying a national income tax (at all) and pays an EU income tax. This is used to pay for welfare in any member state. Each member state can then use sales taxes to provide top-up funding to cover the disparities in cost of products, etc. For welfare, you only get the EU amount unless your state wants to top it up - and they only have to do so for formally registered residents of the state.
Ergo, a removal of the economic incentive to travel from point A to point B for more welfare. Improved wages in point B would be offset by higher costs of living.