Within the context of Ireland, I would have to say that the best thing about the EU is that takes away and reduces a country's sovereign power.
That's assuming that the European politicians and officials who would be making the decisions instead would be:
a) more competent,
b) not ideologically blinkered, and
c) not looking out for their own countries' interests at others' expense (specifically our expense).
After what we've seen over the last couple of years from Berlin, Paris, Frankfurt and Brussels, I think those are big and probably unrealistic assumptions.
Bad and all as our home-grown clowns are, we can at least kick them out.