Bethany: Sacrifices potential healing for more charges. Usefulness depends on active item.
Eve/Whore of Babylon: Decreases the chance of useless red heart drops when trying to maintain the half a heart (full heart on Eve) of red heart health required to keep Whore of Babylon's ability active.
Tainted Bethany: Sacrifices potential blood charges for more health. Overall, still a beneficial pickup.
Tainted Magdalene: Due to the "in your face" gameplay of Tainted Maggy, soul hearts will not be as useful up until the later floors.
Interactions
Keeper/Tainted Keeper: Nearly useless, since all hearts are converted into blue flies anyway. The only use is contributing to the Seraphim transformation.
50% / 
33% of converting any 
Red Heart pickups that spawn into 
Soul Hearts instead.
This item belongs to the 
Seraphim set. Collecting three items from this set will transform Isaac into an angel.
???, 
Tainted ???, 
Black Judas, 
Tainted Judas, and 
Tainted Forgotten: Decreases the chances of useless red heart drops, which these characters can't pick up.
Bethany: Sacrifices potential healing for more charges. Usefulness depends on active item.
Eve/
Whore of Babylon: Decreases the chance of useless red heart drops when trying to maintain the half a heart (full heart on Eve) of red heart health required to keep Whore of Babylon's ability active.
Tainted Bethany: Sacrifices potential blood charges for more health. Overall, still a beneficial pickup.
Tainted Magdalene: Due to the "in your face" gameplay of Tainted Maggy, soul hearts will not be as useful up until the later floors.
Keeper/
Tainted Keeper: Nearly useless, since all hearts are converted into blue flies anyway. The only use is contributing to the Seraphim transformation.
The Binding of Isaac: Rebirth
