Empire frigates are tanky. The engineers are slow, but can survive for very long periods of time. If unflanked and in cover, they can stay alive with half the enemy team focusing them. LRFs don’t quite have that amount of survivability, but if they stick with the team, or stay on the edges of the map, they can stay alive quite easily, as well.
Jericho frigates are different. The guards, all other things being equal, have more survivability than their federation counterparts. With an adaptive build, combined with the guard heals, they have some serious staying power. The LRFs are considerably more squishy than their Empire equivalents, but they also have two other things going for them: One, the fact that the guided torp is much easier to use than the disintegrator, and allows them to flush enemies out of cover; and two, the fact that shield tank regenerates naturally. This makes them much easier to use as an assault class, letting them flank and suppress the enemy at the same time, while also encouraging a sort of hit-and-run playstyle, since the shield is easier to take down, but also easier to repair.
Fed frigates are fast.
The engineers are as fast, if not faster, than the other two factions’ fighters. Since engineers typically get focus-fire’d quite a bit, this means that they have the ability to easily stay with their team, which can make the enemy team think twice about pursuing them. This makes them several times less likely to be left behind for the enemy team to pick up than an empire engineer.
The guards can be as fast as the other two factions’ fighters, but that’s not the point. Guards don’t usually get focused as much as engineers, but the extra mobility still lets them stay with the team easier. Given the fact that AOE and recovery is basically every guard module ever, this means that fed guards can more easily combine both their modules and their team to either defend or attack. Interceptors swarming your engineer? Fly over there and use your modules. Pushing towards an enemy frigball? Fly over there and use your modules! This sort of mobility makes the fed guards a bit more versatile than their jericho equivalents.
However, both fed frigates only really show their staying power when using adaptive shields. Two or three adaptive shields, and suddenly it’s twice as hard to break through your shields. Combine that with a source of healing, and suddenly your hull can tank almost as much as an empire ship can. Now, the tankiness is comparable to both Empire and Jericho, but your speed is still much higher. The only problem with this is if a tackler, guard, or recon slows you down, or if an ECM uses stasis on you. But since Federation frigs have more mobility than other frigs, it’s more likely you’re with your team, which can help defend you against such threats.