The problem with walkers is not having four mana but having four mana spare after you create a board in which a planeswalker won't just die
(Dont apply Weakness and Resistance for Benched Pokmon.) MMC - Steel Wing 150 During your opponents next turn, this Pokmon takes 60 less damage from attacks (after applying Weakness and Resistance)
Cards by AKIRA EGAWA Frequently Asked Questions How can I obtain the Electivire with 2-Diamonds rarity from the Mega Shine set
Or if you sacrifice Flagstones of Trokair to the Field to ramp a Plains, netting you mana in the process
While the mana cost is somewhat more difficult to pay (although WW may be nearly as difficult as B/W in a variety of strategies), the first ability is, for most intents and purposes, strictly better than Elspeths
Considering this deck doesn't usually end games with a gigantic finisher, clearing the board so that you can attack with your "average" characters is critical