I sell a few different Tactical Flashlights in my store, Chief2k Marine, and have tried different ones while on patrol duty as a Suffolk County Auxiliary Police Officer. These are just a few thoughts about what I have found:

I'll be the first to admit these lights are expensive, but their quality is unsurpassed. Any of these lights will last for years and years.

A switch on the tail cap is very important, as it gives better control over the light and allows for momentary operation quickly and easily. All three lights have this feature.

One of the best prices for 123 lithium batteries can be found at the surefire website. I have no connection with this company, just passing on the info. Many people are turned off, saying the batteries are too expensive to use these lights on a regular basis. If you buy them 2 at a time at the local drugstore, this may be true, but in small quantities online, they are very affordable. They also have a 10 year shelf life, so you needn't worry about them going bad. 

I occasionally carry 123 batteries, also at competitive prices.

The Hellfire is the brightest of the three, at 150 lumens with fresh batteries. The downside is that it goes through batteries rather quickly. You can expect about an hour of run time, but the lumens drop as the batteries run down. The (removable) prongs on the bezel are a nice feature and combined with the bright light for disorienting an attacker, make it a good defensive weapon. Those prongs will easily break a car window (if a car stop goes bad) or if you need to get out of a wrecked vehicle. It can be weapon mounted, but I can't find a pressure switch for it to operate from the trigger. The clip is good for keeping secure in your pocket or shirt. If you're using it for police work, it should be on your duty belt, but again, I haven't yet found a holster that fits it. It is a very high quality light and should stand up to alot of abuse. 

The Falcata is similarly priced to the hellfire. There are two models, the 6 volt (2 batteries) and 9 volt (3 batteries) It is also a high quality light, and puts out about 80 lumens. The output is the same for the 6 and 9 volt, but the 9 volt has a longer run time. The body is the same as the Gladius, but without the sophisticated electronics. Blackhawk makes a nylon holster for a duty belt, but only the 6 volt fits in it. The 9 volt is too long, but it does have a clip similar to the hellfire. Lastly, should you have a problem, Blackhawk is known for their outstanding customer service.

The Gladius is the most expensive of the three, due to the electronics it has. With this light, you can go from max power, (80 lumens) down to .8 lumens. This is good for doing paperwork in the car without killing your night vision. The battery life is also greatly extended at this lower output. There is a strobe feature which is good for disorienting, they claim it works well when dealing with an aggressive intox. (gave me a headache) I haven't tried that yet, but I'll let you know. With so many features, the Gladius does take a little getting used to. It's not complicated, but if you're using it for police work or in a tactical situation, it's operation must be reflexive. I kept it on full power most of the time. (car stops, searches, etc) When in the car, you're not under any kind of pressure and can lower the output to complete your paperwork. There is also a nice lockout feature that prevents accidental operation. The Blackhawk holster also fits the Gladius.