I don't find the STG to be that great of a rushing gun. True, you'll get a few kills with it pretty easy, but it's not my favorite to pick and run through the enemies respawn on Fault or Citadel. No doubt the STG is a great gun, but with only a 30 round clip, its hard to rush the enemy and not get mowed down on a reload.
That's why I use the mk-48 with front grip and pistol laser

. Nice 100 rounds that go where you want them to.