Should I have my development site in a subfolder or another domain?

Hi - I'm hoping to set up a BP-based version of an existing site. I'm currently working on a temporary IP address that requires a trailing slash. Wordpress does not seem to like this as it constantly removes the trailing slash from its links resulting in a page not found error. So I'd like to either set it up in a subdomain or in the root folder of another domain altogether. Which is the best option??

Thanks

Duncan