Briefs can sort of... get in between your scrotum and inner thigh, which causes irritation. The other problem is it forces your genitals to protrude, which has just become uncomfortable to me and not good looking. I mean I couldnt wear briefs and then a pair of pants, there'd be a massive bulge. I never got briefs.
Boxer briefs are great, it stays on and doesn't flutter around unnecessarily. It can give just the right balance between not having to slide my genitals to the side but still not having it bulge out too much. Generally more comfortable.