Quote: "How similar is Dark basic to Playbasic and how easy is it to transfer code? "
That's a pretty subjective question, as it depends on the type of features you're using. If you're working on the bare bones BASIC stuff, then you can pretty much cut /paste rename, between them.
However, beyond the basic functions, it's
much simpler porting 2D DB code to PB than vice versa. Since PB includes many linguistic features neither DB/DBpro have.
Quote: " Playbasic is optimized for 2D game making and as far as I am aware has no 3D capabilities, whereas DB is optimized for 3D and although it can do 2D, it can be a little on the slow side. "
While PB is largely 2D oriented, country to popular belief, you can add 3D support to PB today! Just using the COLDSTEEL engine wrapper (DX9/Shaders etc). You just include it and away you go.