Here is an example of what I have heard most often referencing the topic at hand:

"The sub has all the power because they can use their safeword and stop the Dom at anytime. Therefore, the sub is in control.”  

I do not think that statement is logically sound and, at the risk of sounded a bit blunt, it is ignorant. Frankly, in the context of which I have heard this statement made, the informants have been snarky, petty and almost always submissive.

Pardon me whilst I play devil's advocate:
Is there no power in the swat of the dominant's hand? 
Is there no control in the placement of whatever tool the dominant is using? What if the dominant decides to ignore the use of a safeword?

By the way, this statement is also logically unsound and ignorant:  "Dominants have all the power and control."

The questions above are not simply meant to be answered. I have used them to spawn some

interesting conversations in the past, as is my hope here.  What about this?  I know that TBK likes being warmed up when she is getting spanked. Sometimes I just feel like smacking the shit out of her ass though. Do I have the power to do that?  Yes. Do I have control over her when I do that?  Yes. Do I think about her wants and needs before I do that?  Sometimes. 

What if I choose to push her to the point of using her safeword without her knowing my intentions? Who is in control then? Who has the power then? The words power and control both have dominant connotations and are used quite often in ultimate ways pertaining to the Dominant/Submissive dynamic. In the end, the answer will vary from relationship to relationship. 

I believe in order to have a successful and healthy Dominant/Submissive dynamic in a relationship; it must be based around a core of mutual respect, rather than power and control.  In fact, I prefer not to use power and control when defining my relationship with TBK, either to myself or to others.  Have I used them?  Sure.  In some cases they are the best descriptors.