It's the same thing, just with your hands not tethered to each other.
No it's not the same thing. One is Wii the other one is resembling a controller. If what you're saying was the case, why would the Grip even exist then? You could just sell the Pro Controller and skip this odd half-step called the Grip.
Just to further point, none of the people in the trailer use the Wii setup at home.