The newest DBS kills the A9S in throw, and still beats it in overall brightness. However, the spot may be too focused - the CL1H w/ smooth will give about the performance of the DBS w/ OP in a much smaller package, although it will be a bit ringier.
In general, I've heard amazing things about Dereelight. Best quality build, fit + finish, output, regulation... I think the only thing they can improve right now is to come out with a CL1H that's a centimeter or so shorter.
I have a Tiablo A9, and I wouldn't recommend it to mount on a gun. Not that I have any experience with gun mounting flashlights, but the Tiablo doesn't seem sturdy enough. There's a bit of rattling when I shake it, and the parts don't fit quite right. Namely, the emitter is slightly off-center (I asked for a replacement module but it was off-center too, although better), and the O-rings tend to get cut up by the threads. However, it is lighter and stronger-bodied than the DBS because it uses T7075 aluminum, but I don't think you'll ever need any more strength than the DBS has.
Like I said before, I don't have any experience mounting flashlights on guns. So while I know the Dereelight wins in brightness and I know Dereelight's UI would be perfect for the job, the body shape may not be ideal - go with LifeNRA and Strauss' advice on that one.
The MRV is far dimmer than either. Only look into it if you don't think you'll need as much light.