You should also look at the Cloud Defensive Rein 2.0. Even more expensive (but the blems are usually in the ballpark of the Surefire / Arisaka price) but it is an excellent light and I would say it’s currently one of the top (if not the top) performing lights out there.
Better still, the REIN 3.0 is "dual-fuel" capable, running from either an 18650 or CR123a batteries. Streamlight is fine for utility lights but they're not super durable and the switches are suspect. They're like going to Walmart and buying the best tool in the tool dept. Surefire is a step up for sure, more like going to Home Depot and getting the best tool they have. Elzetta & Cloud Defensive though, they're like tracking down the Snap-On truck. A consumer probably can't get anything tougher. Anything made by man can break of course, but it takes stunning punishment for those last two. I once had a Surefire Nitrolon LED light roll off a 7' foot shelf onto a hardfloor and break, totally dead. Could be fluke, but their construction doesn't match that of Elzetta, Peak, CD, etc. Surefire uses a "conformal coating" on the electronics, essentially a spray-on coating like epoxy that helps hold things in place. Elzetta, Peak & CD fully pot theirs, meaning backfill the electronics with a high temp resin. They're much more difficult to break than a Surefire.
This kind of mirrors the $5,000 scope discussion. I can acknowledge that a Nightforce or Schmidt & Bender are better than my Nikon but it's not worth the considerable sacrifice I'd have to make to own one. Good optics are better even for plinking, but I can't justify an expensive scope. However, my main HD gun wears an Aimpoint CompM5 and a Cloud Defensive REIN (the original, just haven't had time/opportunity to get the 3.0 yet) and another wears a CD OWL. For me a $5k scope would be a luxury where I view the carbine in a similar vein to a fire extinguisher- a lifesaving tool. So it's worth the money to me.
Still, financial reality can be unyielding. I'd say Surefire is the lowest quality light I'd put on a defensive weapon but they're not cheap. Maybe the best way to go if you can't spring for a high quality dedicated WML would be to get a quality mount designed for a 1" flashlight, then mount a quality handheld to your rifle. The weak point of a Streamlight is the tape switch. You could get a single output Surefire for, what $80 now?
TL;DR- The Cloud Defensive REIN/OWL lights are amazing. Modlite is very good if you like the color temp. Surefire is plenty good enough but not the SotA anymore. Steamlight is okay if it's all you can afford but not really a step up from Fenix or Olight (which to be honest are pretty solid lights for Chinese brands).