Today I was going to wear my GD-100, but the 4th hole from the tail end of the strap was too loose on my wrist and the 5th hole was too tight. My G-7900 on the 5th hole fit perfectly, equivalent to 4-1/2 on the GD-100. Having different models of G to choose from allows me to get a comfortable fit at any time, rather than one that's too tight or too loose. It's a side benefit of having several different models of G.
Of course, some different models are not different at all with respect to strap fit -- my GD-100, GD-120 and GA-100 being identical in this regard. But all of my others are different physical designs.
What I was going to wear.
What I did wear.