So there is an official description of it in Starwars.com
"FIRST ORDER SPECIAL FORCES TIE FIGHTER
A two-seat strike fighter used by the First Order’s elite Special Forces pilots, the TIE/SF boasts weapons far more powerful than a standard TIE, combining laser cannons with a heavy turret and warhead launcher. Special Forces TIEs have hyperdrives, deflector shields and high-yield cells that provide additional power to onboard systems. These versatile attack ships are used for everything from reconnaissance to combat operations."
So....
....Sensors slot?
Would we rather a Turret upgrade slot or a straight up rear firing arc?