The solid modeling approach is a good way when all you deal with are solids.
However if you do not have only solids it seems very limited in what you can do with it.
Here is an example:
Cloth iron body with a water spout tube in front: Spout is a BRep made by a TS object. I added some Caps as a Base feature but cannot join anything with the BRep of the spout BRep
I really have to start in DM mode add my TS object convert to Breps patch in the open caps join the patches into solids.
Then when I start the time line I can mix the object together - like adding a fillet command after the combine feature - and go back in time and move the spout solid
But here is another draw back of the parametric env without patch tools. It limitis you only to mixing solids.
Here I started right away inside DM and used the split, unstitch and loft command to build a custom blend between the spout and main body resulting in more control.
https://drive.google.com/file/d/0Byzv_NlyKp_2TnZfTWFVamxzMkk/edit?usp=sharing
But what I cannot do is move any of those objects like the spout rotation or the cylinder which cuts the cloth iron open and then let Fusion reapply the blend command.
Here is a video from Alias showing how I sketch curves and create surfaces, project the curves onto the surfaces trim and everything updates when I move the input curves.
https://drive.google.com/file/d/0Byzv_NlyKp_2Vm9yRk5wZlFrWFk/edit?usp=sharing
sorry the alias crashes here is a screenshow where I added a blend command and moved the right circle you see everything updates well.
I hope this makes clear why I think also in the design time line this is imperative to have.
You cannot only work with solids.