So i'm a little bit confused about trinkets for my 5 shammies and was hoping to get some help.

I have a choice of 3 trinkets:

Xi'ri's Gift
Icon of the Silver Crescent
Battlemaster's Audacity

Here is the problem- if i use the first 2, i can get any bosses down that i want, they apparently stack. BUT- i always see people use the second two when I check out armories. My spell damage unbuffed using the second 2 is like 930. Any ideas?