The FN P90 is a weapon for Engineer class, can be purchased for 500 credits for 1 day. It has more recoil and less damage in close range than the MP7, but has less damage dropoff at longer ranges.
Close range 23-27
Medium range 18-22
Long range 10-14
The P90 has somewhat bulky iron sights which obstructs the view a bit. Though it is still usable at longer ranges when fired in bursts.
It has less damage dropoff than the MP7 and PP-2000. However, it can be difficult to use in longer ranges because of its lower accuracy and obstructive iron sights.
The main advantage of the P90 is its large 50 rounds magazine with 100 rounds in reserve, allowing the player to spray around a bit before needing to reload. However, be careful since it has 4 seconds reload time, similar to assault rifles, so it is best to reload when it is safe to do so.