A lot of the time that extra base toughness will offset the mana cost over Connoisseur in terms of keeping it alive
On the other hand, we played against Mono-Black Auras, which was overloaded with Dead Weights and Mire's Grasps, and it felt like we had zero chance of winning (in part because of the amount of removal our opponent had and in part because enchantments get around many of our sideboard cards, like Miscast and Seasoned Hallowblade)
You gain control of a creature, but if you dont allow your opponent to draw a card, you have to put three stun counters on them
You can (theoretically) wait until the very last second before the next Set Mastery comes out to get the next sets Mastery Pass, and you wont miss out on anything
Together, they keep your hand full and your board growing, all without slowing you down