I’m pretty sure interest in Gundam Musou is waning if not depleted since Namco Bandai released this as Dynasty Warriors: Gundam in North America last year. However, Gundam Musou is pretty unique beyond the license mashup, it’s the only game developed originally as a PlayStation 3 only game to get a PlayStation 2 port in the future. Gundam Musou Special beam sabered its way into stores a few weeks ago and we have a decent comparison between the two releases.
I say decent because YouTube videos are far from an ideal solution when you want to compare graphics, but I think watching the two clips gives a feel for some of the differences between the versions minus any extra content.
The PlayStation 3 release is the top video and the PlayStation 2 adaptation is below it.