What we do know is that all the above cards have one key similarity
Nahiris Lithoforming Nahiri's Lithoforming is the only mono-red card here, and it allows you to get rid of excess lands you might have, enable landfall or Scapeshift combos, and more
This card prevents your opponents from swinging out at you with a board full of creatures, and forces combat to be one-on-one, both of which favor you
Song of the Dryads will enchant any opposing permanent and turn it into a Forest, so from Academy Ruins to Gaea's Cradle and from Commanders so they won't die and get recast, Elspeth's, Sun's Champion or Consecrated Sphinx, nothing can answer
The best removal spells can hit more types of cards and keep them off the field by destruction or exile them
Since this is one of the few cards in Oath of the Gatewatch that does not make you exile one of your own creatures in order to use the ability, definitely makes this my favourite card for Two-Headed Giant