Both Blender and Fusion have pretty steep learning curves, so you will have to dedicate a significant amount of time to get to the point where you can just sit down and go from an idea you have to something that is of use whatever you choose.
But.
The thing is that Blender and Fusion do not even exist in the same universe. If your goal is to make mechanical parts it doesn't help you to learn something that is only good at creating meshes. Just as there is little point to learning Fusion if you want to create 3D characters for, for instance, animation.
Everyone tends to start by making shapes, but if you are making 3d printed mechanical parts you soon realize you have to graduate to learning how to do CAD in general. If you are making mechanical parts you tend to deal with precise geometry and geometric relationships. It is usually 2D geometry that drives most of the design. CAD models are often also parametrized so that you can change dimensions, angles, multiples of features etc.
But.
The thing is that Blender and Fusion do not even exist in the same universe. If your goal is to make mechanical parts it doesn't help you to learn something that is only good at creating meshes. Just as there is little point to learning Fusion if you want to create 3D characters for, for instance, animation.
Everyone tends to start by making shapes, but if you are making 3d printed mechanical parts you soon realize you have to graduate to learning how to do CAD in general. If you are making mechanical parts you tend to deal with precise geometry and geometric relationships. It is usually 2D geometry that drives most of the design. CAD models are often also parametrized so that you can change dimensions, angles, multiples of features etc.