+Dedicated Map Control.
+Movement speed is 3.38
+Extremely high potential DPS, 20 (30 Vs Light) damage times 8 max possible targets in a line.
-Creepers make Lurkers fairly useless, because Creepers can bounce from the frontline to a base to defend than back to the frontline.
-Not much use on the front lines other than to deal with pesky light Terran infantry being healed, but Swarm Host contains do this fairly well.
+HIGH Single-Target Damage. Great against armored units.
+Dedicated frontline support unit.
-Potential DPS of Impaler is significantly lower than Lurker.
-Not much use aside from frontal assault. Not capable of solo defense.
I went with the Lurker, damage output helped a lot better than I think Impalers would have, combined with my other choices.