The guys down on the red site sure did not want to take this one on, so lets see what we can do here.
The answer is: It depends. What are you cutting and what are the conditions. In clean dry normal crops, they will probably be close with the edge to the 1460. When conditions get gnarly, the 7700 will keep going.
You are going from an apple (walker or axial) to an orange (walker or axial). Basic rotor vs walker, which will work best for your conditions.
Just saw your earlier post, you have two 7700s and cut beans and corrn. It still depends, on what works for your operation. In most of your conditions, it would appear the 1460 would have an edge. Check with your neighbors.
That is what i meant by conditions getting gnarly, weeds or moisture, will shut down the early underpowered rotors, and even many later models in the toughest conditions. If you really want to upgrade a few years and maintain productivity or increase it, my suggestion would be to stay with a good walker.