At this moment there is no diffrence exept the choice oof t2 factory they can build. What if you could make some diffrence... For example making the bots ablo to travvel on the seabottom and build navel structures as well (would instantly also create a more need for torpedo's). And for the tank fabbers give them more hp (like their heavy armored tanks). So tank fabbers would be less vulnrable to small raid attacks. That's just an example but it would be fun if there is at least some diffrence between the 2...
At the moment T2 bot fabs are greatly superior to tanks due to having more speed. If we want to make a change, each should be to buff the T2 veh fabs to make them distinct. Option 1: Increased HP. IMO this won't cut it, any fabber caught in the open is as good as dead no matter what. Besides, having high HP is a role best left to bot combat fabbers. Option 2: You could give veh fabs significantly more range, to increase survivability when placing aggressive structures, and compensate for slow speed. Option 3: A slow acceleration but a very fast maximum speed for crossing large planets faster than a bot counterpart. This would have the side affect of making pelican micro less mandatory for quickly expanding on large maps. This is my favorite option.