Lets think about what efficiency means.
"Accomplishment of or ability to accomplish a job with a minimum expenditure of time and effort."So being efficient implies being fast (no waste of time) and minimizing movement (minimum espenditure of effort). So in the context of a reload, which is more efficient?
Option #1 certainly seems faster and to require less effort than option #2. So according the definition of the word, Option #1 is the most efficient.
Now lets talk about Effectiveness.
"Adequate to accomplish a purpose; producing the intended or expected result."So to be effective the technique just has to accomplish the goal and produce the intended result. It doesn't say anything about being the fastest or least wasteful. I think instructors/shooters who teach/use the over the top rack technique do so because they believe it to be more reliable at accomplishing the goal. Right? I have never seen an argument for using the over the top rack technique say anything about it being faster or requiring less movement and/or effort, it is always about being able to reliably manipulate the gun.
So for those of you out there who espouse the over the top rack technique, effective might be a better word to use instead of efficient. Just sayin'.