but Blitz3D only naturally deals in 3d coordinates so you have to write your own system ( or use one of the libraries available ) if you want to think purely in 2d coordinates.
Blitz3D can do 2D just fine out of the box, however it's not going to be as fast as a good 2D in 3D system or indeed as fast as BMax.
I do however recommend BMax over B3D, it's a much more advanced and flexible language.