The number one benefit to me is that it's spring mounted to the feederhouse. In my hills the auto height was to slow on a regular flex header and would run into the ground. Thing to watch is that the springs on the adapter are adjusted correctly so you get the proper float. When the header is set up correctly it cuts great. If it's not it will leave alot of beans in uneven ground.
We bought a 974 a few years ago because it was cheap. We had just been running a new JD flex draper. After running in edible beans where low cutting is of the essence we were sold. Since have added a FD70 but the 974 cuts just as low. The FD floats a little better. The biggest negative is the narrow throat opening especially if you're feeding a wide body combine but just fine on any single axial rotor. Also not the best in dessicated canola because of that narrow opening. Great head overall really.
I need to take back what I said about a 974 not working well in dessicated canola. Running right now and it's working just fine. Just have to remove the upper cross auger. It blocks access to the feed drum for the crop coming in. Only time I have ever seen those cross augers do something is in very hilly terrain.