There are several posters on this site that are going to be able to provide more than I can, but since i’m the first the to the party, I’ll add my experience. First, I see no reason, given enough skill, why you wouldn’t be able to fabricate everything that is cast. You could sit down and carve a block of metal just like you would a block off wax.
Secondly, the major limitation you’ll run into is the ease with which you can use additive methods to build-up areas or correct mistakes. There is an amazing fabricator on YouTube, scaffoal, who doesn’t use wax and is able to fabricate complex shapes that I personally would have done in wax. But, he’s a hell of a lot of fun to watch and I’ve stolen more than one technique from him.
Lastly, the majority of the pieces I create are fabricated. I find I am able to achieve better symmetry in metal than I am in wax. My lines are cleaner and I don’t have to take into account shrinkage. I enjoy it more than I do wax. Wax is faster, though. I’ll often start carving a piece in wax to get a sense of the design and then switch to fabrication because that’s where I’m able to achieve a higher quality piece.
The important thing is to make sure that you don’t get caught in the mindset of this way is better than that way. It seems like I see that too often in our industry and have been guilty at times of furthering that sentiment. A mentor of mine always said, “there are nine ways to do it and they’re all right.”