I've used a bunch of different ones with a Photon and N750A Pulsar.
The pic below shows 4 different ones starting from left:
Sightmark 850, Evola 850, Streamlight Tac IR in 850 and a standard torch with 940 pill installed.
The Sightmark (same company that makes the Photons) has two power levels and adjustable focus.
The Evola has 2 power levels and infinate focus.
The Streamlight is one power and one focus.
The torch on right has one power and set focus.
The Sightmark has proven to be reliable but on the weak side. Still performs well out to about 150 yards. Bonus: works for days on 2 AAA batteries. Runs about 50 bux.
The Evola has proven to be the best of this bunch. Adjustable power and focus lets you spread out the light at 100 yards and doesn't spook pigs when done this way. Will also focus down and you can see a long, long way. Down side is it requires 18650 batteries which OK for me as I have lots of stuff that uses that battery. Runs about 35 bux.
The Streamlight is the most powerful but will spook game at 100 yards due to overpower. I found the best use for this light was long range scanning or just point at the tree tops at 100 yards and you can still see pretty well down low. Uses same 18650 batteries. Runs close to 100 bux.
The torch with 940 pill works well at 50 yards but not much past that. It presents the best picture but due to limited power, distance is lacking. It also takes 18650 battery and is same power rating as the Sightmark and Evola. I think I have about 30 bux in this one.
The Streamlight is well made, pretty and powerful - too powerful for most of my use and just sits on the shelf.
The Sightmarks are now used on my hand scanners and will really light up a Gen2 unit when it gets dark.
The Evola finds it's way onto my 6.8 pretty much every time I go out. They have this version which is the smallest one and also a much larger one that takes two batteries but I see no need since this one "sees" further than I care to shoot at safely at night.
Bottom line, bank for buck winner is Evola - I've packed this thing thru rain, fog, and many trips and it still just works.
You can pay big bucks for a Streamlight or Sniper Hog unit and the Evola will trounce them at about 1/3 the price.
Also, don't let "brand names" fool you - almost are all made in Chinese factories and if you buy as few as 100, they will lazer engrave YOUR name on them.