Stay. EU immigration is unequivocally good for the UK. Leaving the EEA would be unequivocally bad for our economy.
The people wanting to leave are mostly disgruntled nationalists with power fantasies and delusions. They think we'll leave the EU and suddenly be a world superpower. They think immigrants are taking their jobs, when really they just can't get jobs because they're stupid. They think Britain would still be an Empire if we hadn't joined the EU. It's all a bit pathetic really. We have a representative democracy precisely to prevent issues like this - uninformed masses making decisions they can't understand the implications of. We shouldn't even be having a referendum.