1) "Best" Focus policy depends on screen real estate, because screen real estate helps decide...
2) Window layout. How many pixels per window are there? Are your windows tiled or not?
3) Desk clutter and the presence of mouse real estate. (People have mentioned this) -- if your mouse has a high probability of getting bumped, then this will effect your focus preference.
My point is this: If you have a small screen, and non-tiled layout, and a cluttered desk, then you are more likely to prefer click to focus. Why?
Because the probability that an accidental mouse movement would change focus in a pointer-focus system is large enough to require some sticky focus mechanism, like click-to-focus.
Think about it. If your mouse never moved accidentally, click to focus would be unnecessary, because your focus would always stay where you last left the mouse.
So why does the Mac and Windoze use click-to-type? Because they use small screens, because they sit on main desks (probably more than special computer desks), and because they were initially conceived as single user, single tasking systems. All of these factors tend to favor click-to-focus.