welcome to WebmasterWorld, Bryan!
in general it would be best to use the domain that is performing best and in fact use the same urls after transitioning, especially those urls which are getting referred traffic.
you should also implement a 301 redirect of any non-canonical url requests to the canonical domain and path in a single hop.
revisiting the domain question:
- you might consider other issues affecting the value of your domain selection such as if the domain name matches your brand or if it is a short or memorable domain.
- there are additional issues to consider when selecting a domain on a ccTLD versus a gTLD if you are targeting a worldwide search audience or geotargeting.