Marksman. Marksman is good for medium and long range due to its 4x scope. It's mobility is also good, which enables you to move faster. The State Defender, however, has low damage, ONLY 2x scope and lower mobility. But the SD has a bigger clip than the Marksman.
So, go for Marksman..
It mostly depends on your taste for combat.
You like being fast and like long-mid ranged combat, go for the Marksman (AUG)
You like not worrying about ammo, close-mid ranged combat, and only need to buy the gun, no upgrades Go for the SD....card