Wading into the debate here, as I've had my fair share of "light adventures", especially over the past 6 months. I'm a big proponent of having a useable light that works for your purposes on all rifles that you own.
@Jigstick, at your budget tier, a $150 Streamlight will likely perform adequately and sufficiently. Are they the "best" solution? Maybe not, but they hit your budget tier, and are likely durable enough to withstand your uses while performing the illumination task. A buddy of mine likes his Streamlight just fine that sits on his suppressed MK18 clone and has gone through probably north of 12k rounds on the rifle with the light mounted. Actually, he just told me that he hasn't had any problem with the Protacs when shooting unsuppressed or suppressed . I'd say . He did recently upgrade to a Modlite 18650 on one of his uppers, and a Surefire 640DF on another MK18 clone upper that is identical. His choice wasn't based around the Streamlight's performance, and he still runs Streamlight Protacs on other rifles that he has and likes the light.
OP, do you have any requirements besides price point? Target ID via a red dot or an LPVO? Indoors, further away outside?
@JC0352's questions are super-pertinent to your light choice, and should be the driving factors behind your decision.
Here's another factor to the discussion that may or may not matter to you: If you don't care about the type of batteries that you're using, then CR123s are likely just fine, but my personal preference goes to 18650 and 18350s. AAs still have a place, but unless you have a logistical reason for selecting a weaponlight that uses them, then they're not really relevant to the weaponlight discussion, just my opinion.
I have briefly used an Arisaka/Malkoff combo, and if you're willing to spend a bit more money, they perform well. I really don't have much experience with them though, so I can't comment on them outside of "they work reasonably well from my limited experience". I haven't ever heard bad things about them or that they were inadequate though.
Ok, so on to the much higher budget (like, 2 to 3x your budget) options:
The Modlite lights perform as advertised, are highly modular, and are extremely rugged. The PLHv1 heads are a great step up in output and performance from the Surefire 640DF, with the PLHv 2 heads being magnitudes of power (in useable lumens and candela) above the PLHv1 and every Surefire Scout series light that I've ever used, period. The PLHv2 eclipses the PLHv1 in output by a noticeable margin, which is impressive to say the least. Output is a double-edged sword, however, as face and eyeball melting output can also affect you. Anecdotally, I actually like the Streamlight's output, and find it is reasonable and adequate for illumination indoors. Again,
@JC0352's questions should really drive your light selection. If you're looking at a beam that really does reach out in distance, the Modlite OKW head performs this extremely well. I haven't had the opportunity to compare an OKW to the Cloud Defensive OWL side by side, but the OKW has noticeably more "reach" than Surefire heads, Streamlight heads, and the PLHv1 and PLHv2, if being able to ID targets is of interest to you.
The Cloud Defensive OWL is probably my favorite light in terms of output and beam profile - it's just awesome - if the REIN is anything like the OWL concerning the actual performance of the light and beam profile, then it's worth saving up for and holding out to upgrade. Is it expensive? Definitely, but I view a good light as critically important on any rifle. You cannot positively identify what you cannot adequately see, period.
Another option is to purchase components for these lights on the secondhand market, which shouldn't be extremely difficult. Do keep in mind that if you're looking for an option that gives you access to an extended mount, a pressure switch/mount, and a tailcap, this is going to add up in price very quickly. That little illumination device and a way to activate it hanging off of your rifle will, depending on the components, cost you north of $400. In this way, the Streamlight Protac packages are actually pretty great, in that you get a useable light, pressure pad, and mount for under $200. For comparison, you'll spend $108 on a Surefire ST07 tape switch and UE07 tailcap alone if purchased separately new.
Notice that I didn't really mention Surefire? There's a reason for that: I used to own a number of Scout series lights from them, and, while they have a great brand and perform really well, for the price point, they kind of come off as a lackluster option by comparison to some of the other options on the market for my purposes. That doesn't mean that they are bad lights by any means, and herein lies an opportunity: Surefire Scout series lights will be on the secondhand market for pretty reasonable prices, which is a great thing if you like Surefire as a brand and trust them. Also, all Surefire Scout series tailcaps, pressure pads, and most of the aftermarket mounts for Scout lights are compatible with the Arisaka and Modlite 600 series and 300 series bodies; In other words, you are already buying components (outside of the light body and head, generally speaking) of a future, more powerful light if you want it, and those components will likely retain their value and relevancy on the secondhand market if you want to sell them.
Hope that this helps your decision, and good luck!
