I spent a year at a really fancy french culinary school. I didn't finish but that is another story for another time. One thing I remember is that one of my instructors said you should never use a rotary whisk to beat eggs. he swore by a whisk only.
It had something to do with the speed and the angle of the whip. Frankly, it seemed pretty silly but French chefs know how to blow things out of proportion. I have had lots of scrambled eggs made with a rotary beater and I probably couldn't tell you what they were made with. An egg is an egg, not that complicated.