Lets try to keep this on topic, and here is the point of this thread:
3D Overworld:
Pros:
+ Unique (not many pws have it)
+ Looks cool 
Cons:
+ Requires houses to be npcs (lags)
+ Cant make cool stuff as easily as tiles (bridges, house interaction, etc..)
+ No matter what you do, its going to look similar to GK.
2D Overworld
Pros:
+ Can do many cool things easily
+ Doesnt lag
+ Matches well with the houses (no 2d on 3d)
Cons:
+ Almost every single server has a flat map
As you can see, both sides have their good points and bad points.