I love mecha games and Virtua On is an important part of SEGA's history. Both console ports are technically impressive, real showcases for their systems and were afaik very successful in Japan. I think Twin Stick control is essentiaI for these two. I remember that the Saturn version got bashed badly in the german gaming media because of the complicated controls ... a real shame that those accessories never made it outside of Japan.
I already own the Saturn Twin Stick and the Dreamcast version is, thanks to this thread, on its way to me.
I must admit that my favorite mecha game is GunGriffon 2 though. Of course also played with the twin stick.
I'm looking forward to the arrival of the Gundam Side Story-Collection/trilogy "The blue Destiny" (part 2 & 3 support the Twin Stick) for my Saturn. Judging from some videos it seems to be much faster paced then the GunGriffons.
My favorite Jaguar game is Iron Soldier 2 and I almost bought a Nuon just to experience part 3 in all its glory. I'm also still tempted to buy one of these ugly, chunky XBoxes just for Steel Battalion and its awesome controller