Image - The whole idea of a thermal "image" being a static, linear attribute, that we can compare between devices, needs to be debunked. I notice the "image" thru the UTC-x changing about 3 times as I do my 360s from my normal coop over-watch set up position. This is due to the nature of the terrain around me. I NUC an average of once every 1.5 360 to compensate as well as adjusting brightness (down) and gain (up) if needed. The vast majority of thermal users I speak with seek the ONE MAGIC SETTING for their device where they can "set it and leave it" ... and in my experience that is an unobtainable quest. You must learn to match the setting to the conditions, continuously, if you want to optimize the image. That said, the bulk of the internals between the Mk3s and the HALOs are the same, the cores, the displays the rear lenses. The front lens goes to the HALO.
Also, looking a pics people make of thermal images may or may not be accurate for comparison purposes. Several years back, when the pulsars first arrived, there was a lot of "debate" about whether the APEX had a better image than the Armasights. I myself compared a Zeus 75mm 30hz to a Pulsar 50mm 50hz and the Pulsar had a lot of "shock and awe" in terms of the image. Especially in the first 2-3 minutes, especially inside 300yds. But as I worked thru a multi-week comparison, I began to be able to split out why these differences existed. Two of the highlights. The pulsars, out of the box, auto nucd and lot in the first few mins, the armasights did not. The FLIR cores in the armsights were purposely tuned to "pop out" the critters ... in essence, by default they were higher contrast, which does NOt bring out the terrain as well. And what folks noticed looking thru the pulsars was how much clearer the trees and such were. So there were reasons for the differences and by adjusting the setups on the devices, you can make them look almost identical. So, it was really more about setup than fundemental differences.
Now with the HALOs a slighly better front lens is a slightly better front lens. But is that a strategic differentiator ? Well, between the mk3 60mm and the UTC-x I can see tiny details at 500yds, like a cow's ear flopping around while she is working on a bale at 500yds in the pouring rain. And the magnification difference, I think, overcomes the lens difference as even the UTC-x cannot see the cows ear on 18x on the day scope, any better than the mk3 60mm on 4x digital (18x net). So, I say no. Does it have a "shock and awe" appeal in some of the pics we've seen? Yes. But we know little about how the settings were optimized on either devices and how much they were nuc'd etc. Hence, looking at pics is not a definitive decision making factor for me. I also note that in one recent sequence of pics posted here, the camera itself was contributing to the image blurryness since it was out of focus. And the same thing happens to me. Thru the lens pics are tough.
Controls - Well here, it will be mostly personal preference, though I find the turret system on the mk3s to be the most fool proof in conditions like -20F where I am wearing thick gloves. The button system on the UTC-x (and same on the HALO) can be used in -20F conditions with thick gloves BUT requires more practice/training.
With any control system, you want to MEMORIZE the options you need to use in the field. You don't want to be reading menus and deciding what to do next. You want to think about the result you are after and pound the necessary buttons (or knobs or joysticks) without thinking. So, once you get to that level. The differences in the control system disappear. The only exception I can come up with is the heavy gloves exception ... and that perhaps the joystick is slightly easier to make a mistake with due to needing precise amount of pressure to activate a change. But I use the joystick, the turret and the button system all multiple times per week and I would consider such differences to be a very minor contributing factor to a purchase decision as they all work and you can learn them all.
History - The HALOs do not have a history in the field yet, since they are new. All new devices generally have teething troubles. But we haven't heard much about such for the HALOs yet. So either they tested the sh^t out of them and they have less. Or the folks that have them so far haven't put them thru enough paces in the field yet to shake out the issue.
Value - If we line up list price and focal length for all the REAPs and the Mk3s and the HALOs .. the "price per focal length" metric goes slightly to the HALOs. But again, I wouldn't make a purchase decision on that. I would pick my focal length based on the terrain I am usually in and the ways in which I am trying to use my device. Like I consider the primary purpose of my mk3 60mm to be a long distance SPOTTER. I just mount it on a carbine so I can shoot if needed. It is a "weaponized" spotter
... but the ability to PID out to 500yds and beyond in terrible conditions, like pouring rain, etc. Is my use case for the mk3 60mm and I'd rather have the extra optical magnification on the front end, than a slightly lower price for a 3.5x unit.
Maintainability - For me an important factor is the ability to keep the units up and working. And here, the HALOs may be equal or superior to the Mk3s/REAP but we do not know. It cannot be known. There is no track record.
I've sent my mk2s/mk3s in twice. Now I was upgrading them, but I also had Trijicon address issues. Working with the same folks both before and after the merger was a plus (unlike the experience with the Armasight/FLIR merger). And expectations on return time to me were set but exceeded in both cases. And the "dead pixel growth" issue I had in the mk2/3 has not returned for me. There are zero dead pixels in my mk3 or patrol and both of them have been used in the field every week for years.