Whether to include one card over the other comes down to specific environments, and larger Cubes could certainly facilitate both, but the point is that Callidus Assassin is a very real card for control decks that would like to spend their turns leaving up mana for counterspells and removal
In gameplay terms, she costs 3 Ink to play, has 2 Strength, 3 Willpower and 1 point of Lore
But rather than clog up this list with cards like Elspeth, Storm Slayer, Exalted Sunborn, Doubling Season, Peregrin Took, Xorn, Academy Manufactor, Worldwalker Helm, and others, I want to give other abilities the spotlight
Best of all, Gyome can even protect the creatures you do want in play by giving them indestructible until the end of the turn
The current flavor of the month is Basking Broodscale
Short, sweet, and has deep enough abilities to provide strategic and synergistic options in other cards