There were a lot of different options when we were building "United Assault," the mono-white deck. The Pro Tour Guilds of Ravnica featured the full spread of one-mana white creatures: Snubhorn Sentry, Leonin Vanguard, Skymarcher Aspirant, Hunted Witness, Dauntless Bodyguard, Healer's Hawk, and Rustwing Falcon (aka Trusty Rusty). As the metagame evolved after the tournament, we also saw these numbers change. Notably, Hunted Witness and Snubhorn Sentry set a precedent over Rustwing Falcon as Deafening Clarion became a staple of control decks and Goblin Chainwhirlerbecame less played.
We decided to model "United Assault" off Luis Scott-Vargas's 2nd-place deck from Pro Tour Guilds of Ravnica because it minimized the amount of guesswork we had to do in terms of the metagame at the decks' release. Luis Scott-Vargas's build was the most self-contained and cohesive build of White Weenie and the least sensitive to metagame pressures.
Creature (29)4 Dauntless Bodyguard
Instant (3)3 Pride of Conquerors
Enchantment (7)3 Conclave Tribunal
Land (21)21 Plains