You can not compare them as both of them are beautiful places, . But Neelum Valley tour be from Kutton to Taobat where as Trip to Hunza means covering Naran, Babusartop, Chillas, Hunza all the way till Khunjrab .
For neelum from Kutton to Taobat can be done easily in 3-4 Nights.
From Islamabad to Naran, texilla Haripur route is prefered by divers mostly, maybe because VIA murree you will have to climb more height which means less fuel avg. or face traffic .