Dig,
The groundhog is bigger and heavier, but also slower and more timid. When confronted with danger, it's nature is to run away.
I don't know what it would do if cornered. I wouldn't want to find out. Their teeth are formidable. I haven't seen these barn cats hunt as a pack yet. They seem to be solitary hunters. I also don't know what the mother groundhog will do if the babies are threatened. I don't know if she will defend them or not.
It 's going to be interesting to see things play out.
Steve Thomas