Kind of depends on the size of your shop and what, if any, other activities you do in the space, or items that you store in the space.
For my home shop I have found that attempting to use a single large fan to evacuate air from the entire shop building was not so useful. But then I do multiple disciplines in my shop. I've found that a single fan for the whole building evacuates the smoke, fumes, grinding dust etc, but also all of the heated air. Further, said fan drags the abrasive dust, paint fumes/particles etc across all areas (tools, benches, other items) of the shop in the process.
In short, for my situation, I wish that I had put in duct work and used a system of spot pick-up hoods at the point of process. As in an adjustable pick-up hood over the weld table, and one over the large open bay for large weldments, etc.
If you are truly only doing fab work in that space, and not concerned with having a layer of abrasive dust and paint particles on just about everything, then a single large fan would probably be fine.
Edited to add: also I've found when doing a large weldment (like the hay feeder I fabricated) the whole shop fan was not as effective at evacuating the smoke as I'd hoped it would be. But in this case I had tacked the whole thing together and then it was a marathon welding session.
