Okay, so, I don't have 3dsmax to hand, which would really help me make this case.
I also primarily fly [LN] ships, which makes this post probably very bias. However, before you ask, I have flown the Nephthys, Guardian, Titan and Avenger recently in combat.
I've noticed a discrepancy in the Nephthys when compared to the Guardian and the Avenger, namely its turn stats according to FLstat. Here's all the relevant stuff:
Guardian
11000 hitpoints
68 b/b
1.1750 max angular speed (radians/sec)
0.4835 time to 90% max angular (seconds)
11400/1160 powerplant
5 guns/1 turret forwards
Avenger
13200 hitpoints
72 b/b
1.1220 max angular speed (radians/sec)
0.4717 time to 90% max angular (seconds)
15000/1340 powerplant
5 guns/1 turret forwards
Nephthys
14500 hitpoints
78 b/b
1.1707 max angular speed (radians/sec)
0.4717 time to 90% max angular (seconds)
15000/1340 powerplant
6 guns/1 turret forwards
Titan
13500 hitpoints
73 b/b
1.1220 max angular speed (radians/sec)
0.4717 time to 90% max angular (seconds)
15000/1340 powerplant
6 guns forwards
Now, to be honest, I can't see that being justifiable, given that it's so much better than the Avenger while having a similar profile. A profile which the Executioner shares, which Ursus decided to make a thread about somewhere else here. In fact, it keeps up with the Guardian as well, despite having far more hull, regen capacity, power and an extra weapon pointing forwards.
I put the Titan in as well, as it's an example of a fighter that is pretty hard to hit compared to the big ones with the wide wings, if I'm being honest. Sure, it pays for that by being a munitions magnet, but oh well. Personally, I'm not seeing the justification for the Avenger being as poor as it is when put besides the Nephthys, especially without the shape "advantage" of the Titan.
But there we go. I heard that someone was bleeting that the Avenger was overpowered, and I invite those people to spend some time in the Nephthys.
Indeed, and if things were balanced according to the lore, then the Eagle would be worthless put against a military ship, such as a Chimera. Like with fairness and equality, you can't have both at once.