I’ll echo what others have said on Teferi, great signpost card.
I’ll push in favor of Elspeth though. Aggressive decks are becoming faster and more resilient (or at least can be if you want them to), so I am okay giving control powerful tools to fight back. Especially in White which is notorious for not having good 6+ mana value cards, I really like Elspeth as a control signpost and pull to the archetype.
Being mono White also opens the door to Boros and Orzhov control too.
All that being said, if your cube has so much ramp that you can cheat her out reliably, I’d avoid her. On turn 6 sure. Turn 4? Too much!