Why do you assume it is a medium resolution? Almost no games use medium resolution, I could darn near name them all from memory. Now if it is Virtua ANYTHING then it is medium res, otherwise it probably isn't. Just post the title of it and I can tell you.
Also you are going to want to hope it isn't a medium res, arcadevga doesn't do medium res, and medium res is the absolute worst choice for mame, it is very difficult to set up (must use dos and advancemame and do a lot of praying), and the results are that 98 percent of your games will be running on the wrong monitor, but paperboy will look really nice.