While white isnt the best color for counters (thats green), or for reanimation (thats black), or even for Equipment without red, it takes firm second place for all three , allowing you to build to make Zack a star
Calhoun comes loaded with two abilities, Resist +1 and a neat special ability called Level Up
So, if your opponent deals you damage, they become monarch, and you cast another Azure Fleet Admiral, you get the monarch back
Combine that with Ripple (good luck getting multiple copies), Recover (a very weak mechanic) and Rune Snag cycle, you just don't have a good likelihood of opening something relevant
If a legendary permanent or an artifact entering or leaving the battlefield causes an ability of a permanent to trigger, you also get to trigger that ability a second time, so you can double up on any benefits that you get from these cards, so its an invaluable asset