Some seats are better on a plane than other ones, for many possible reasons. Check to see which seat you should ask for on which type of plane of which company.

But, remember the word POSH -- it stands for Port Out, Starboard Home.  It goes back to the days of ship travel in the British Empire, when it was much more desirable to be on the north side of the ship on the way to and from the colonies in India and Australia.  On that side you do not have the early morning sunrise shining though your porthole, nor the late evening light keeping you awake.  It's still true on airplanes crossing the Atlantic, but "port" and "starboard" would have to be read from a North American perspective rather than a European one.