The smaller and lighter sigma 18-50 2.8 is appealing to me, however, I can get the 16-55 used for close to the same price as the sigma lens new (there aren't any used version where I am located). So that is a consideration in my mind. If the lens is too big and doesn't work out with my shooting I am hoping that there is decent resell value if I decide to downsize at a later date.