While Ruby/Amethyst probably has the advantage realistically in that matchup, its not by a lot and a strong Sapphire/Steel player can certainly overcome Ruby/Amethysts tools either by gaining more cards in hand through superior draw support, or discarding that decks key cards via A Whole New World
Both can be really onerous at times, so you want to ensure you wont get hated on
In conclusion, while these last three spots are pending a gameplay verification, I felt the most confident putting Anticausal VestigeAnticausal Vestige as the most powerful warp card, simply because I couldn't see any downside
Unfortunately, like Zac, Billy has left Wizards to do other things
Grafdiggers Cage Grafdigger's Cage is among the best graveyard hate cards in Commander and beyond, but it works well as a stax piece to prevent library shenanigans
and Mei from Turning Red