Man its hard to add anything to what Bill said. As usual he says in a few words what it takes me volumes to get 'round to. I'm just lucky these cats tolerate my ramblings...
Another thought that comes to mind in all this is that the Minelabs are from Oz. Not that I have anything against Australia or Australians in general, mind you. A rather civil and friendly lot, in my experience. It is just that service from Garrett, should it be needed, is fast, courteous and on the spot. I have heard horror stories about M-Labs...
Also, and again, no offense to our Aussie friends, but American dollars can do more at home that abroad. Besides, the Garrett GTI 2500 is as capable as any of us will likely need, especially for the casual and varied use you will put it to. Friend Bill there has even done some reporting on it's capacity as a nugget shooter!
When you listed your normal hunt sites, you essentially gave a description of Charles' Garrets design parameters for his detectors!
If it were my money, it'd be the Garrett. Course, I'm biased...