Funny, I think the exact opposite. To me, FWHM does not mean anything substantial while it's clear what the standard deviation is. You are raising a sociological point here. It's true that FWHM is common in the neuroimaging community, and that's probably because it was promoted by SPM, but I would really assume that the vast majority of statisticians, machine learning and even signal processing people are rather unfamiliar with the FWHM.