Same skill 1, way better skill 2. The really big thing is the shields will absolutely stop the hit that breaks them, so they can take a Goliath to the face and be absolutely fine as long as their shields were up at the time. Also, you get damage reduction for having more units left. The main thing to note about them is they lose their offensive stats (considerably worse RoF, slightly worse Firepower) in exchange for this tankiness, so you'd better have the rest of your echelon be tanky.