Glad you ask. There are claims by every cue maker but no testing. Since you are going to be hitting a stationary object ( the cue ball) with a stick you want to know its compressive strength, when you are hitting with the tip. That will tell you how long it will last. If you use English (twisting the cue ball) its bending strength would be good to know.
If you plan to keep it looking good for a long time, you look at its hardness. A problem comes up with fancy cues that have a lot of added things. Most a glued in with Epoxy. Heat will made Epoxy move and cause the inserts to pop. Cold will made Epoxy brittle and crack. Epoxy failure originates at a point of stress concentration and at flaws.
If you plan to keep it looking good for a long time, you look at its hardness. A problem comes up with fancy cues that have a lot of added things. Most a glued in with Epoxy. Heat will made Epoxy move and cause the inserts to pop. Cold will made Epoxy brittle and crack. Epoxy failure originates at a point of stress concentration and at flaws.