This decision is different. We are choosing the framework through which we are to be governed, not the programme for government. The consequences of this decision will significantly outlast the careers of any politician you can name, and will also outlast the economic and social issues of the day. It will not change the polices that we vote for, but will significantly affect how they are implemented, and how effective that implementation may prove to be. As this is a constitutional question, the majority of 'Facts' spouted by either side are pure speculation, as they all pre-suppose subsequent election results.
This is not to say that questions of policy are not important, but policies can be changed, potentially quite radically, as future governments are installed. The system under which policies are implemented is much more fixed.
European government is much more diffuse and necessarily consensual than our national government is. As a result of first past the post, we have a national political system that almost inevitably produces strong government, that can take radical decisions, and has a clear identifiable leader.
Europe is not like that, as the constituent countries are not prepared to cede enough sovereignty to legitimise an overall leader. Instead, decisions are effectively made by committee, and vetoes ensure that significant decisions are approved by all.
Europe has no obvious leader, and no true president. With no legitimate single centre of power, decisions have to be made with broad support, or (frequently) not at all. This means that policy, when and if decided, will represent, roughly speaking, a midpoint between the views of the 28 countries involved.
The effect of this is to drag any policy area where Europe has influence towards the political centre. When 28 parties all need to come away with something from the table, the chances of a radical decision being taken are very low. Instead, any decision will reflect the middle point of the inputs. Whatever the electoral cycles of individual countries, the pan-European average doesn't move much. Furthermore, when a true crisis blows up, like the refugee crisis, or the Euro crisis, the strong, potentially unpopular-with-many decisions that so clearly need taking, are not possible, as for a European decision to occur, all parties must agree. There cannot be losers. Conversely, this mechanism can be a safety valve on dangerous decision making. The whole project was initially designed as a method of preventing further European conflict, by putting the mechanisms of war (coal and steel) in a political environment that could not be hijacked by an out-of-control national government.
It is much easier to list the failures of this form of government than it is to list disasters that were avoided by it. One cannot list crises that good government prevented ever manifesting, but the track record on making Europe a peaceful, stable, and liberal place for its citizens is undeniable.
This centrist and cautious tendency is currently a frustration for the British right, who are not able to act as radically as they would like. But it would be a mistake to frame the referendum either way in such partisan terms. Should a left wing government be elected in the UK, they would similarly find themselves unable to go as far as they would like, as they would run into centrist obstacles on intervention in industry and competition rules. See how Greece's left failed to extract any meaningful changes to austerity, even with a profound national mandate to do so. The EU is, and will remain inflexibly centrist, and incapable of making radical decisions. It is a fundamentally constitutionally weak system of government.
So the question for us is how strong do we want our governments to be, and how radically do we want them to be able to act?
This question applies both to governments you support and governments you do not. If you want your government to be more radical, a vote to leave would also liberate a government you strongly dislike to act more radically. A vote for out, is a vote for strong government that can make radical decisions, whether you like them or not, and whether they are good decisions or not. A vote for in is a vote for weaker government, that is less flexible and less capable of responding to situations, and also less likely to make dangerous, stupid, or unmandated decisions.
The right answer here may depend on circumstances. One could argue that when times are good, diffuse European government protects us from over-reach and unnecessarily radical intervention, and in times of crisis, prevents an adequate and appropriate response. In a sense, it becomes a judgement call on what sort of future you for see for Europe and the UK, and how directly and effectively you would hope governments could respond to future events and issues. Stability against flexibility. Safe stagnation against a risky gamble on the future.
Whilst the decisions we make with regard to trade, rights, travel, and immigration etc, are extremely important, governments can be changed at subsequent elections. The system under which they implement their policies most likely cannot. Significant constitutional reform rarely happens more than once in a lifetime, whilst general elections are usually once every 5 years. This is the longest term decision we are likely to be given for many decades, and the consequences will live with us through governments we can't imagine and events we can't predict. We should pick the system that we individually believe gives us the best balance between protection from bad decisions and nationalistic folly, and the ability to respond effectively to challenges and crises. The correct point on that scale may be different for different people. The debate on more tangible issues is valid, but only when conducted through the prism of how this significant constitutional choice will affect the implementation of policy.
Anything else, in or out, is total speculation.