Only played Skies of Arcadia for about an hour before my Dreamcast broke, but I didn't really care for it based on that. I really, really love Valkyria Chronicles.
This one is really off-target. Valkyria Chronicles was made by mostly the same developers as Skies of Arcadia, but it wasn't a spinoff. It's an unrelated game where the appearance of Skies of Arcadia characters can be described as cameos.