Originally Posted by
Ldnn1
Yes you can choose either, assuming you're only coming for tourist purposes. If you're planning on doing any work/volunteering etc I'd say you should enter as an EU national.
Not to be that guy, but it shouldn't matter what document you enter the UK (or any other EU country) with. As a citizen of the EU, you will have whatever work/volunteering rights in the destination EU country regardless of the nature of the document you used to enter.