I have all manner of reducing backs for an 8x10 and a 4x10, and I usually prefer to begin with the larger GG. especially if movements are involved... it's a way to see the "big picture" and also for the practical matter of seeing what's happening to my image circle (i.e. to watch out for vignetting etc.).
Of course, the thing about habitually using reducing backs for smaller formats is that you then are lugging a whole lot of camera! And the larger GG is that much easier to break. Mind you my 8x10 is a cambo, which is heavy as hell... I don't have a dorff.