What are the advantages and disadvantages of a brittle materials?

Malleability & Brittleness might be considered as trade-offs on a scale.

The more bendable and resistance to breaking, the more malleable.
The higher resistance to bending, the more brittleness.

Glass has some tremendous transparency and resistance to bending, but it carries the risk of breakage.
Kitchen ceramics have great temperature resistance, reasonable durability against forks and etc. Easy to clean. Yet, dropping them can be traumatic.
Tools are perhaps one of the most critical applications... Too much malleability and they bend which may weaken them and lead to breakage anyway. Too much brittleness, and they snap, often at moderate danger to the mechanic. Files, designed to cut steel require tremendous hardness (brittleness) in order to keep their edge. Drill bits also need a very hard tip. And, without it, they are worthless... Too soft and the tip just rounds off. I've got some Chinese bits that I can bend with my hands... and when I couldn't get a hole drilled with them, I gave up and had to find something else. But, again, the risk of the hardness required in a drill bit is that they will snap.