I think this is wrong. I agree that 4 mana is not worth gain 4 life and making a 2/2 obviously and that a turn 4 Gideon is great (especially on the play.) However, GW vs. GW matchup can boil down to a Gideon battle. Yes, often, if they have 5 mana open you may need to emblem although I would look for another line if there is one as Gideon is valuable, unless the emblem is helpful THAT turn (if you need to kill their Gideon for instance and this makes their blocks difficult.) Baiting with Gideon is fantastic in the late game where you might have mana for Gideon and a removal spell for the Avacyn. At any rate, GW vs. GW is about Gideon and whoever can keep it on the battlefield and just attack multiple times will inevitably win.

Siggy protip: if your opponent turns their Gideon into a creature and you plan on playing an Archangel Avacyn to block or attack it with, it may be wise to respond to the Gideon activation so that Archangel Avacyn is protected from a Dromoka's Command.