If one wants a broad gene pool, a German wirehaired pointer has a broader gene pool than a Drathaar (if one asks Drathaar breeders, they are not the same). If one were to go to NAVHDA tested lines for either shorthair, wirehaired, or a griffon one would find strong hunting lines. The griffon is probably the most improved breed over the last decade because of NAVHDA testing. Shorthairs and wirehairs still make up the bulk of the dogs testing and the breeds with the best percentage of prizing. These are some of the points in favor of testing ones dogs, the wirehaired pointing griffon was almost extinct as a hunting dog and testing (not the outcross to the Czseky Fousek) brought the breed back. NAVHDA and the breeders deserve a slap on the back.
To answer the questions, the griffon, when well bred, is a good upland dog and a good water dog. If we are comparing a griffon to a Ches in the water, the griffon lacks, but what doesn't. If the water is real cold, the answer is a retriever. The upland pointing and flushing breeds don't have the fat to handle the cold water. A neopreme vest will help immensely. If waterfowl in cold water is a large portion of your hunting, I would strongly suggest a Ches, Lab, or an American water spaniel. These dogs have the coat (which is important) and build (which is more important) to handle the cold. The wirehaired pointing breeds have the coat just not the build.
Dr Fatguy