Why would you test drive a Hyundai if you knew you wanted to buy the Mazda ? (maybe that’s a more like-for-like comparison, as I don’t think the G80/G120E are worlds apart, unlike the Porsche Plus I’m not saying which is which ;D )
… and the SOC vs SOM option can have a big impact on the size of your device. Plus, with the G80 you MUST use the ENC28 for Ethernet, where the G120E does not.
But there are lots of other differences, but they are usually things that matter to a specific application - do you get enough IOs for what you need or can you trade that off for a smaller size.