I wonder if anyone can offer any advice? I currently have a forum using vBulletin, and I'm about to convert to IPB.

At present, our forum is at url/forum/ and we have IPB installed (for testing etc) at url/invision. We're going to pay for conversion, and support have said that whilst doing it, they can move the new forum into any directory.

So my question is, when it comes down to SEO, which will do the least harm.. over-writing the existing forum, so it remains at url/forum/ or keeping it in a different directory, such as url/invision?

I'd appreciate any pointers.