have both the FDL and the FGS. I agree with the common theme of responses in this thread that the two ships are not comparable because they are so different from one another. A more comparable ship to the FDL would be the FAS, which I also have an FAS. Although you would think by nature of the design differences between the two ships that the FDL would handle better than the FAS, it is actually opposite. The FAS will turn on a dime under boost, while the FDL under boost seems so over powered from the inertia it gets stuck in the forward direction from the momentum requiring you to wait for the ship to slow down before being able to maneuver. Due to the limitless maneuvering under boost, FAS is probably the best handling mid-range combat ship in the game. I say that without bias towards the FAS because in fact I actually love the FDL and do not like the FAS. However, it is hard to deny the ship due to its functionality and practicality. I know that the FDL already received a boost to its Power Plant, but to remain competitive within that range of ships, it needs a boost to its Distributor to a 7 size as well if you like to use laser weapons for the medium hard-points. The FAS can fire almost twice as long as the FDL when equipped with 2 large lasers and 2 medium kinetic/thermal weapons. While that is an unfair comparison, the FDL requires the use of all 4 medium weapons to stay effective, and in order to preserve your stay for longer periods of time in any NPC combat instance, you will need lasers in those medium hardpoints. They are both already proven ships in PvP, but I cannot speak to their effectiveness personally in PvP because I stay away from PvP entirely. In PvE both ships are proficient in any PvE instance, RES, CZ and Nav Beacons.
The FGS shines in RES zones and falls flat on its nose in CZ instances because of its inability to effectively maneuver in the CZ and maintain the the pace of the NPC ships. The FGS is better compared to the Anaconda than it would be the FDL. It almost seems like a smaller version of the Anaconda when it comes to its firepower and its similar but lighter handling, albeit having a greater mass than the Anaconda. The FGS is perfect for RES because of its sheer firepower, but it also appears from videos I have seen on YouTube to be very proficient for land based missions that require you to attack installments. This is particularly the case when you equip the ship with dumbfire missiles that destroy installment defenses in one shot outside their sphere of attack and sensors.
Therefore, if you are looking for a ship to dogfight, you are probably better off with the FDL or the FAS. However, if you are looking for a ship simply to overwhelm NPCs through sheer firepower in any RES or even Compromised Nav Beacon, the FGS is not only a great ship for that purpose but it fights like the Anaconda while being a little more limber. Personally, I love the FGS, and it was the first ship that I bought when that expansion was released. However, the FDL is definitely my first love, and I have had that ship since I could afford its purchase. Here are my builds for each ship for reference (bearing in mind that my FAS build is for multi, so it has Cargo Racks and Planetary Landing Module):
FGS:
http://coriolis.io/outfit/federal_g....AwRj4zNEg===.Aw18cCMVA===?bn=Fed Gunship v01
FDL:
http://coriolis.io/outfit/fer_de_la...325d5566.AwRj4yrI.EwBj4yIRnI==?bn=FDL 1.5 v02
FAS:
http://coriolis.io/outfit/federal_a...02v66b.Iw18cQ==.Aw1-gjJQ?bn=FAS Multi v01 1.5