Saviour43
To be frank, The Jegan is a more advanced model, most with beam rifles as there fire arms, the Doga varies with beam weaponry. But then again, beam weapons aren't the only thing that make a machine superior. I think it depends who pilots.
Actually, the Geara was first seen after the Jegan XD
It's just a simpler design to ease production, and use a multitude of weapons to make up for its lack of innovation/advanced technology.