Another mission to the outer planets?

I was reading a bit on Ur' Oberon and we noticed that we have only been able to photograph one hemisphere in 1983. That seems like our knowledge of the icy giants and their systems is awfully limited at the present time. Would the benefits of sending another probe to the outer gas giants be worth the cost of such a mission and what would be the benefits of another probe going to ur and neptune aside from mapping and a bunch of cool pictures.