I'd say it depends on your area and goals.
For our businesses, my father and I ran our shops away from the house to keep people from using our home as an extension of the garage. However, it adds a security requirement of some sort, even if it's just blocked windows and good doors.
For a personal shop, being away allows you to be a bit more "smelly and messy" within acceptable reason, it also allows sort of a man cave for fun car events, especially if it's got some size. I originally looked at buying or renting something in a commercial area, and almost signed a pretty affordable lease in a nice building that had 10 or so separate shops, but I felt it would make working on my own stuff feel more like a job and decided against it, not to mention the cost of renting without ownership.
We are in the process now of buying another home with land and potentially with or building a big outbuilding for both fun and income after I retire from the military in approx. 3 years. It will be at my home, but intend a completely separate entry to make it clear when I am "not there" or working on my own stuff.
That being said, I really like cinder block buildings if in decent shape. Fire concerns are low, "feels" like a shop to me, and the price looks real nice. In addition to security, I'd be most concerned with the condition of windows, overhead doors, roof (big), concrete floor, and heat/air conditioning. All of those can be pretty expensive and annoying if below par.
