Its death is an evil death: This means that when a person meets death as a result of vicious talk, it is an agonizing death. He suffers through a long period of pain, mental if not physical, before death comes.
And Hades is preferable to it: Hades is the world of the dead (see the comments on 14.16). The author is saying that a person is “better off dead” (Good News Translation) than going through the shame, embarrassment, and pain caused by vicious talk.
Contemporary English Version‘s model for this verse is much clearer than Good News Translation‘s model and will be helpful for many translators:
• Cruel words cause suffering
worse than death itself.
Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on Sirach. (UBS Helps for Translators). New York: UBS, 2008. For this and other handbooks for translators see here.