I have to be careful here because you all know that I am a Fusion Newbie. That said, my roots go all the way back to the very first 2D only CAD systems that were designed mostly to replace drafting boards, and I progressed through to Catia which is the tool of choice for the aerospace industry and the majority of auto makers. So despite my Fusion newbieness, I feel like I can make a few relevant comments.
Perhaps the most important comment I can make takes significant effort to explain. It goes back to a time when I went to California to visit with Silicon Graphics (SGI), in preparation for buying a few dozen SGI Workstations for a next generation Catia Design Studio we were pulling together. During my tour of the SGI operations, I was introduced to their resident staff psychologist. Among other lesser jobs, his primary responsibility was to ensure that their hardware and software was designed and optimized to reflect the way people think and do things. The physical AND the mental ergonomics of a computer workstation if you will. I was only supposed to meet this guy and then move on to other highlights. But I loved every second with him so much that I ended up staying an hour. His insights were amazing. Among other things, he explained why I cannot remember names or numbers or formulas but can remember faces and places and mathematical relationships. He simply said, most people have a 2D mind. They easily absorb and remember data points like names and numbers and events and formulas. You have a 4D mind. Data points get lost in your mind. You don't see data points. Your mind is a continuum of processes and relationships that are constantly changing like a mixture of ingredients stirred in a pot. Sometimes great bread results, but more often its just a mess nobody would ever want to eat. It was an insight I never would have realized without him. Just like the psychologist at Steelcase whose job was similar (that's the pilers and filers story), this guy insists that we all think differently. The human mind is not a machine or a computer or a duplicator. We all think we know how we think but we are usually wrong about that.
The classic HP calculator RPN is a good example. In our minds, we don't input a number and then multiply. In fact, we can't multiply until we have a second number. The operation follows the two operands. In other words we write 4x2=8 but we think 4, 2, x = 8.
It's the same with design. Good design is a synthesis of experience, knowledge, imagination, and innovation. It is not a computer tool that generates an automatic prescribed output based on a prescribed process.
The best CAD tools shouldn't force a user to follow a defined procedure, it should allow the user to execute a design he sees in his mind and the process of getting there should be intuitive and natural, not prescribed.
That was a very long winded way of saying that some people are comfortable with designs that are based on lines, vectors, curves, and other foundational dimensional parameters that are infinitely small. Some people want to start with non dimensional globs of solid shapes like blocks, cylinders, and spheres that are dimensionless in the beginning but are refined later in the process. And of course, there is a continuum of choices and methods in between. The final choice between which approach (or blend of approaches) is best is really just a reflection of how we prefer as individuals to put what we see in our minds into our model.
There is no right way or wrong way. There is only what works best for each of us, each in our own way.
Words cannot describe how delighted I am to learn (thanks to
@PeterT ) that Catia can be used by starting with sketches, and (thanks to
@Janger) that Fusion can be used by starting with solids! Both are empowering and reassuring to me. I now see a very bright light in the tunnel ahead of me.
If only all these tools could be more intuitive and user friendly. Then again, I never did learn to make decent bread.
Sorry to be so long winded. Merry Christmas Everyone!