To me it is all about how you use it.
One option (controller) is when you use a PC that is dedicated to run the machine - say like Mach3 - you actually run the machine with it.
The other is the DSP - which you drive the machine via it's DSP system -so you need only a file that it can read to work the machine. The AWC708C by definition is a DSP system part.
I am not good with electronics = but I have found on th net something that may shed more light on this: http://electronics.stackexchange.com/questions/3067/what-is-the-difference-between-a-dsp-and-a-standard-microcontroller
Since to me it is about the operation - this is why I askd for help from memebrs, to see what is thier experience with it.
I have already a CNC machine with a controller - so if I don't get more info I will go for the DSP - at least this way I will be able ti research and learn something new. . . it may be even a new mistake