The upside would be that you'd be able to run bigger calipers if you ever needed or wanted to, and less sidewall = more stability, although you want enough sidewall to get decent flex also. I run 16x8's on 4.25BS because I wanted to run 285's, which are 33x11.5 in size. A lot of 16" tires are D-class also, which means a stiffer sidewall, but I don't know if a stiffer sidewall equates to a stronger more cut resistant sidewall as well.