Having Mirrors of website

Hi i was just wondering if someone has a .com a .co.uk site is it worth copying the content so it is on 2 seperate websites???

Or is it better for the .co.uk site to be transferred to the main.com site when a person visits.

I basically mean is it better in terms of SEO rankings and also localised marketing OR does it confuse customers????

What is the best option???

In terms of SEO rankings it's best to keep them both separated and preferable with different content.

I don't think it confuses customers :)