INTEGRATED GRAPHICS VS. DISCRETE GRAPHICS
The main draw of the Surface Book is that it can be configured with a discrete NVIDIA GPU. This makes it more powerful than the Surface Pro 4 for intensive creative tasks like photo and video editing, as well as gaming. You can also turn the screen around and use it like a creative canvas, without sacrificing any graphical processing power because the GPU is located at the keyboard base. That said, the integrated graphics on the Surface Pro 4 is no slouch, especially the Intel Iris graphics that's on the Core i7.
With the base removed, the Surface Book becomes a powerful, but still thin-and-light 13.5-inch tablet; or in Microsoft's own words, a portable clipboard. Unless you need the bigger screen, we think the Surface Pro 4 is a better choice in this use case. This is because in tablet mode, the Surface Pro lasts up to nine hours, but the Surface Book just three. The Surface Book does get up to 12 hours when it's docked to the keyboard base.