Building from my previous questions:
I want to evaluate performance of both MapServer and GeoServer. Can both servers exist on the same machine (each serving out WMS) or should I set them up on separate servers?
You can check out this site with detailed comparison of Mapserver vs. Geoserver http://www.esdmdata.co.uk/mapserver-and-geoserver-and-tilecache-comparison-serving-ordnance-survey-raster-maps
You can install both of them on the same system; You just need to make sure that they use different ports.
So the defaults should work just fine, as long as you don't have something else running on these ports.