The GDK has its pros and cons, as does DBP.
DBP is the easier language without a doubt, but C++ has the advantage of being object orientated, it is faster and the MS IDE is a nice development environment.
The plug-ins that are avaiable for use with GDK are DarkPhysics, DarkAI, DarkShader, DarkLights, EZRotate and EnhancedAnimations.
There may be more, but the above are all available.
Personally I would suggest the GDK if you have the patience to learn the language. I own DBP and GDK, I use DBP to prototype ideas, effects etc... Once I have tested it I then port it to GDK, they compliment each other nicely.
Who is your Daddy, and what does he do?