If MJ, Rising Star is dealt lethal damage at the same time that you gain life, she won't receive a counter from her ability in time to save her
But the card drawing Fortunes one is clearly the best of the cycle, due to the sheer, raw card advantage that follows
Using an indestructible creature to block a lifelinker will still result in the opponent gaining life, and blocking a creature with wither will still cause -1/-1 counters to be placed on your creature (which could actually kill it!)
Of course, a card that packs this much Lore comes with a cost while Mirabel costs only 5 ink to play, she cant be played unless the player has five or more characters in play
Speaking from the uninformed perspective of someone who's never opened an Unfinity pack, the set looks like it would be fun the first time you tried it, and then never again (outside of an Attraction Commander deck, which admittedly sounds like a laugh)