I would say you are wrong.
The linkage is there to give more range. While each different design might yeild a different result.
Its not a simple equation. It is always difficult to convert a hydraulic force from a cylinder into a rotating motion. If you were to create a force graph for curling, it wouldn't be constant. Rather an arc. Near it's limits it would have the least power. In the middle of the range, it would have the most.
Let me give a simple hypothetical. Let's say your current setup allows for 140 degrees of rotation. Which would translate into a given distance, let's say 70" of physical movement at the cutting edge.
Now you add a linkage and give the bucket 180 degrees rotation. That would translate into more movement, let's say 90".
So now you are asking the same cylinder to move a load farther. The cylinder would have less mechanical advantage. Which means less power.
For every inch the cylinder moves, you are asking the load to move farther.