Am I supposed to draw cartoon faces in orthographic or perspective projection?

I am doing exercises from Fun With A Pencil and now I have to draw spheres

And now I have a question - am I supposed to draw them in orthographic projection or in perspective? For example if I am to draw the 2nd sphere in orthographic projection, distances between the axis and the curvse next to it are supposed to be the same, but if it's in perspective projection, distance between the axis and the dotted line will be smaller than the distance between the axis and the line to the left from it.