According to T_Skys excellent frigate guide, the Republic Fleet Firetail is a popular but not especially strong faction frigate, being 3rd in popularity, and 5th in win rate with a faction frigate 1v1 win rate of 43%. Despite what sounds like some lackluster statistics, I think the RFF has a lot of things that make it worth flying.
For one thing, everyone knows the RFF is a little on the weaker side compared to other faction frigates, and so t1 combat frigates are a lot more willing to engage the RFF then they would be something like a Fed Navy Comet.
The fit I am reviewing in this case is an old standby of faction warfare lowsec, the 280 2x web RFF:
[Republic Fleet Firetail, 280 2x web] Gyrostabilizer II IFFA Compact Damage Control Small Ancillary Armor Repairer, Nanite Repair Paste 1MN Afterburner II Fleeting Compact Stasis Webifier Fleeting Compact Stasis Webifier Warp Scrambler II 280mm Howitzer Artillery II, Republic Fleet Fusion S Rocket Launcher II, Nova Rage Rocket 280mm Howitzer Artillery II, Republic Fleet Fusion S Small Projectile Collision Accelerator II Small Transverse Bulkhead I Small Transverse Bulkhead I
There are a few cons to this fit, the DPS is not especially good for a faction frigate at 203 (Heated), and the tank is also nothing particularly special (4.89k EHP and another 2.33k if you can get all SAAR charges). That said, two things make the RFF a real contender in the right type of fight.
The first is that the 280 arty has a low rate of fire, which lets the RFF crash through active tanks with high alpha. The second is that the RFF is a very fast hull, on par with an Atron, and slower only then the Slasher and the Dramiel. This, together with the fact that the fit has two webs give it an enormous amount of range control. This fit is very strong against active tanked brawlers, weaker against scram kiters where the range control just turns things into a DPS race you might lose, and weakest against buffer fit scram kiters where the alpha from the arty does nothing and it is a straight DPS race.
If you fly well, the vast majority of the time you can use the RFFs range control to disengage from a losing fight.
In general for most matchups you want to fly to minimize traversal, and maximize your damage/alpha (for example with a Keep-at-range 7.5 km command). With the range control this fit has if you position yourself correctly and pay attention in many cases you can disengage rather than losing if a fight is going against you.
In most cases I am comfortable engaging all attack and combat frigates, and as you move up to faction and pirate you want to fight shorter range active tank stuff more than you want to fight longer range buffer tank stuff.
The beam Tormentor and the dual rep Breacher deserve mention as fits that can potentially give you a good fight. In both matchups you will want to work to minimize traversal, and be sure to not start reps to late. Against the Tormentor, and most SAAR tanked ship, RF Fusion is a good ammo choice, but against the Breacher consider switching to RF Inferno (so as to not be shooting explosive damage into its active shield tank).
Fed Navy Comets are not too bad to fight if they are fit with blasters, but it is an uphill battle if they are rail fit (the superior damage and tank, combined with the fact that much of the tank is in hull sort of hard counters the alpha from the RFF). Hookbills have the worst of both worlds with buffer tank, good projection, and better tank and DPS. Other pirate and faction frigates will be good or bad matchups against this fit as a function of their tank type (The less buffer the better) and their weapon type (The less projection the better).