Workability. An over the top swing means you can only hit a pull, pull fade, pull slice, pull draw, pull hook. That is still a lot of options and if you throw improper alignment in the mix you can even hit straight draws 'lined up right, pull draw becomes a straight draw and straight shots, 'line up right and hit a pull'.

You can't however hit a straight push, push draw or a push hook or even a completely straight shot for that matter without a slight lining up right coupled with a closed club face. You also lose yardage or proper loft its, a trade-off with the over the top move.'you get both by being on plane' So hitting a high lofted properly spinning shots is difficult because instead of a lot of backspin you get a lot of left to right spin or conversely right to left draw spin if you shut the face down to avoid losing it right.

If you get a chance post a down the line, its easier to see what is going on in those.