Really depends on the program.
GPRs are of course hospital based and you'll see patient, go on rotations through internal medicine, emergency medicine, anesthesia, etc. Some programs can have you on rotation (not seeing patients) for 4-6 months. You also get to cover the emergency room in the middle of the night and sew up peoples facial lacerations.
AEGDs are 12 months, you generally see patients the entire time, usually some course work, and usually more 9-5.
I think in general you may get more time in the dental clinic in AEGDs. Both types of programs do all general dentistry work (endo, operative, etc.)
My personal opinion is that if you come from a school that is weaker in the medical sciences then a GPR (I think) will teach you a lot about managing your medically compromised patients. If you come from a school strong in the medical sciences then an AEGD maybe better as a lot (but not all) of those rotations maybe redundant.
Of course their are many exceptions to everything I've said. Because all programs are different it is very difficult to compare the two. Have to interview at each one and see what you like.