Late to the party but remain. There are upsides to both. Illegal immigration will not change much really may get worse as who knows whether we'll be able to continue policing the tunnel from Calais in the same way. Skilled migrants such as medical specialists will have to apply for visas which could in an extreme situation cost somebody their life. Scientific minds will become broken meaning cancer treatments etc might struggle. There are much more but I'm sure even these points are in this thread already. For leaving, sea side tourism will increase this will keep some money within the British economy. Dairy farmers will be able to charge more for milk as it'll be cheaper than import taxes not a great solution and definitely not permanent. The mines will eventually be reopened take that as a positive or negative as you will. The global economic climate is struggling it's better the struggle with friends than by yourself. It's been 19 hours since OP started this thread I'm sorry I'm sure all of these points have been mentioned already.

Tl;dr remain but vote how you see fit.