When I watch MLG or some other replays, the commentator always says Zerg taking a third vs Protoss's FFE or Terrans' double Command Center is an equilibrium, why?
I think taking a third this early causes more points to guard in the middle of the game, especially when Protoss decides to push and when Terran decides to drop their marines. As a Zerg, I build a Spore Crawler and Spine Crawler at every base, and put some zerglings and Banelings there, but a little mistake will let all my drones die and sometimes I even lost my base.
Someone told me that I must use Muta's to keep pressuring Terran or Protoss to let them be away of me third or even my fourth.
But a few protoss cannons or a few Terran Missle Turrets or pulse marine just keep my Muta's far away from his base, and after a while, his Thor will come out.
So why is taking a third only an equilibrium vs T/P's fast expand?
It seems to be a burden for me. And for math only, shouldn't 3 > 2 so doesn't this means taking a third early should let me take advantage?