You give your opponent a 3/2 creature, though sometimes you dont care at all because its too small
Some can help you win games faster, while others, mostly just look cool, but need something more to see competitive play
If you have a card in hand at the moment the trigger condition occurs, Bloodhall Priests ability wont trigger, even if you can get that card out of your hand right afterward
Either way, you still get to set up your next draw
Second, while Fraying Omnipotence costs two additional mana than Pox, its much easier to splash into multicolor decks, making it more useful to a larger percentage of players
It must be Special Summoned from the hand with three Tributes, but it negates the effects of all of the opponents face-up Monsters