Probably battery life and processor. Apple smokes everything Android, with a battery not nearly as big. Then there's cohesiveness - watching Android chat apps come and go is laughable.
That aside, it feels certainly like Android leaves you with Goldilocks syndrome. You -can- buy phones with great battery life, great cameras, and great software/ui, but not all 3. Pixel has middling battery life. Samsung's UI/software is slow and bloated. Moto has terrible cameras.