I think it depends very much on the case. Some material are very difficult to get procedurally, some others fit better, anyway it’s always longer to get a good procedural material. If you have time , making a good procedural material that you can reuse or tweak is great.
If you need quick , fast and efficient result, generally by using one or two textures from good textures site is the way to go, as it’s way faster to setup . Maybe it should be the first thing to try, and if that doesn’t do the trick then maybe see what you can get procedurally.
You don’t always need to unwrarp, you can look at box mapping.
Sometime you can mix two photos with a cloud texture so the pattern look more infinite.
You can also make the material change according to distance. In some ways , that’s taking best of both worlds…
What I find a bit tricky with image textures , is the bump you get from that doesn’t always look good. Unless you use softs like awesomebump, but again it’s long to get something good, it’s not always worth it.
In the end, I think it’s good to practice a bit of procedural texturing because it can always get useful, but most of the time using textures from photo can do the job.