If any of those shared the same vision as me i would try to join.
The 2 i would probably join,but dont wanna do game logic (game), they wanna leave that to end user beskoped mod's.
so in the end you have 2 simulator engines in progress. like i didnt test both but i think none of them adresses region trade or someting in that mater (regions).
but u are rigth, first project as the road system working and buildings, second one as RCI working, if we joint both we had simcity 2013 already