I should say, I'd rather have both the numpad and arrow key column on the left. I'm right handed. One benefit would is less travel anytime you need to move your hand from your mouse to keyboard and back, as well as those relative distances promoting slightly more even/ergonomic arm positioning.

The other benefit is that I might actually be inclined to use the numpad for games instead of wasd, which would free up the rest of the keyboard for more shortcuts.