The way I look at the two (let’s not get into Categorised/Relevance search yet!) is that Global is like “Finding Something You Put Down Somewhere Safe But Don’t Know Where”, whilst Advanced is very focused and is more the “I’m Looking For The Key With The Yellow Fob And The Yale Logo”… well that’s how I explain it to users anyway 🙂
The limitations of Global are that is is a scattershot approach – you search for a term and it has no filters (but that’s where Relevance Search can help as you can narrow down your results).
You also can’t save your searches, which is a bit annoying if you filter down a relevance search and think you might want to repeat that search again!
One other thing to note is that Relevance Search has to be enabled, it’s not there by default, and can take an hour to populate the index.
Advanced Find in contrast is completely zeroed in on the one primary entity and that’s it. You know where you’re looking for something, and you have seriously granular control over how that search is performed.
Downside is that it can be overwhelming for users who just want to find “Activities sent by Fred in the last 3 months”
I have no doubt there are other Pros and Cons of each – hopefully others will chime in and add to this – but these are the main ones for us.