Generally, I believe someone told me that they're 0.5 inches smaller in each size. And they also have a little taper when compared to the Gio. Gio is more of a slim straight, while the skinnies is a true slim.
No problem at all. Is this on myhabit? I find that a lot of people don't like GBV cause it isn't slim enough, but its definitely slim in the smaller sizes (or at least for me). High arm holes, tight chest, good length. Once again, I think the only complaint is the billowing from the back.
Gitman in slim in the smaller sizes. The only problem with Gitman is that their chest increase from one size to the next is a difference of 2". And the back isn't slim because of the box pleats, but I actually like that look. Gives it a classic feel. Hope that helps.