Though like both Manhunter and SOTL, I never really feel the need to compare or decide which is the best. They are very different movies stylisticaly and thematically.
And Manhunter is more of a police procedeural/thriller than a horror movie. And though SOTL also has elements of a procedeural and highlights the detective elements, it does emphasise the horror a lot more.
That said, would not call SOTL a horror movie at all.