Good info....I was looking at surefire but the price jumps quite a bit. But buy once cry once right.
This will be rail mounted so the one I was looking at was the X300U, agin its a pistol light...I guess I like the compact size of these.
Should I stay away from the pistol lights and get more of a long gun light?
It all depends on your use case and your budget.
Pistol lights can work for sure, I had an X300U on a Mossberg years ago, it did fine. I will say, although it did work, the controls are less intuitive and easy to use on a long gun, as the X300 was specifically designed for it's primary use being infront of the trigger guard on a pistol, so it has the paddle switches on either side for controls.
If you're focused on size, a Surefire M300 Scout, is a single cell version of the M600, so it has a smaller overall size than the M600 and would work better than an X300 on a shotgun but it would have less battery power and output than the M600. Always a trade off.
You can also build your own setup though. I used an Arisaka M600 body, Surefire M600 head, Surefire M600 tailcap and an Arisaka mount, runs great.
Olight will likely work just fine, if you are constrained by funds, but just know what you're buying, as it is a cheaply made Chinese light. I've had multiple Olights fail over the years and so I stopped bothering with them entirely.
Basically, if you want the best option available from an American company then get a Modlite, if you want the very close runner up and most widely used light by Mil and LE guys then get a Surefire and if you are more budget minded, go for a Streamlight. Those are the 3 big dogs in the light world and all work well, coming in at different price points and features. If you are really pinching pennies but absolutely need a weapon light, then go with the Olight.