When should I build mongooses instead of pillars?
Pillars are slower than mongooses, but they are still pretty fast. They have way more health; if you have mongooses and screw up your micro, they are in trouble unless you have parashields, but pillars will be fine. They do have long range, so they can kite, but they miss a lot so their damage at long range is low. They can kill t1 pd, but so can lobos.
What are cool things I can do with mongooses that I couldn't do with pillars? Are there particular units they're more effective against?