This is a landfall mirror, so the game mostly comes down to who builds the bigger board faster. Torpor Orb stays in the sideboard. It only stops abilities that trigger from creatures entering, and landfall triggers come from lands entering. It therefore does nothing to their Mightform Harmonizer, Sazh's Chocobo, Icetill Explorer, Mossborn Hydra or Sapling Nursery landfall triggers, and Earthbender Ascension's enter trigger comes from an enchantment entering, so it is unaffected too. In this matchup it would be a dead card. Instead, trade the slower Esper Origins for Surrak, Elusive Hunter. It is a 4/3 trampler for three mana that can't be countered, and it draws you a card whenever an opponent's spell or ability targets it, which punishes post-board removal like Meltstrider's Resolve and Hard-Hitting Question. Esper Origins is a fine value card, but it doesn't pressure the board the way a hard-to-answer 4/3 trampler does in a race.