It's the Mark Sein from Fafner in The Azure against the mighty Granzon!
Rules: No outside interference
Granzon cannot become Neo Granzon
Arena: Tatsumia Island
My vote: I'm going with Granzon on this if only with his Black Hole Cannon. Now, Mark Sein is far faster and can land more hits (not to mention way more weapons), but aside from the Medusa I don't see them doing serious damage to Granzon. At the same time, Granzon's only other real advantage is his thick, sometimes immune to physical attacks, armor. It's a battle of speed vs. strength, and I'm abstain in favor of Granzon.