the only reason to duplicate is that my current site is very location based. Santa Monica. I get majority of work through this as its high on google so I get enquiries via google every week and I don’t want to jeopardize that.
However it may put clients from further afield off.
Search engines like Google will consider URL’s that point to the same site as duplicate content. They have no way to know that you are “pointing” to the same place, and you can change where it points at any time. Some of the darker side SEO folks use to play a shell game with URLs. Look at one site and build up the SEO rating and switch to another site. This is the reason you need to do redirects with 301 (permanent).