Hi Kuro,
I would recommend asking for samples, then you'll see that the difference in thickness is not visible to the naked eye - I just checked some samples I had received from Aero in the past.
My Happy Days is made out of Vicenza; my girlfriend's MC jacket is made out of the soft black steerhide. The steerhide is really soft and does not need any break-in period. The Vicenza, though in no case a CXL FQHH, is quite stiffer than the steer.
Awesome, thank you. I did have some samples of both the black Vincenza and Soft Black Steerhide, and between my two samples the steerhide was noticeably thicker. However, doing a quick mearsurement of the thickness of the two, the steerhide was a quarter of a millimeter thicker. I forget the exact measurements now, but I believe it was 1.25mm for the Vincenza and 1.5mm (roughly speaking) for the steerhide.
Seeing that evidence and what Carrie is telling me that the jacket will be more snug with the steerhide, it gives me something to consider.
Of course if the the steerhide just works with me, then I probably have nothing to worry about.