How is it almost even in Internet but way behind in phone usage?
Inefficient chipsets.
Oh, and one thing to note: the iPhone 7 is just 750 x 1334 pixels (barely XGA - or progressive scan HD). The other three phones are all 1440 x 2560 pixels - nearly 4 times the resolution. Better than full HD (not half-HD), or WQHD for computer screens.
So they’re pushing 4X the information to the screen. Four times the GPU and memory moves. And they still win in terms of battery life.