0 chance your method is more effective. Because you can mouseover party frames.
For example I can have tank 1 targeted. Cast physick (using my keyboard <t> button>, then instantly lustrate tank 2 with my <mo> button, and then immediately do another physick on tank 1.
The delay from moving your mouse from each person, and clicking them makes it automatically slower.
Now if your talking about on GCD abilities only, it is far less noticeable, however it still lets you make decisions milliseconds faster then any other method even if they are performed optimally, for example for cleansing.
I know its all doable with either method, so it really doesn't matter, but claiming your method is more efficient is naive.