Rear armor, more penetrating small arms. Although I don't know if the damage is negligible or not.The damage of small arms isn't quite negligible, not really apparent with rifles, lots of the shots bounce and the ones that hit take 8 hit points, hardly much. Because of the way burst weapons work (lots of lower accuracy shots paired against high vehicle target size) they inflict actually visible damage on poorly armoured units.
Btw in that part I was replying specifically to the guy who mentioned AT guns.
I liked the rear fire arc, it was actually a really nice touch, made the unit different, and I got used to having to reverse it all the time. I agree Lt tier could use a buff but it's not like AAHT was underused or underpowered before...