Yeah, so I just tried to take another attempt and contrasting the thermal characteristics.
However, I can't get the eyepiece to work with an iPhone on the other thermal device, and even though I have the software, Optics One's software for getting pictures off the thing is relative crap too.
In contrast to that specific issue, FLIR crushes the competition as it was made to work well with iPhone / consumer market.
So, I'm going to explain it:
The full thermal device can do full thermal, and a bunch of other modes. In "full thermal" it get clean images that show very good detail. For example, you can see the studs in the walls, and where the heating ducts are, etc.
The FLIR ONE can do much of the same, but the CLARITY of the picture and the detection of hot/cold is no where as nice. So, where I can see the studs with the "full thermal" device, and can only see some of them with the FLIR ONE.
So, a picture of the 12 foot ceiling in our master bed room (below) only gets a blury image of the poor insulation points at the ceiling. Whereas the "full thermal" device gets the studs behind the drywall, the poor insulation area, the detail of the angles of the part of the ceiling [i.e. the apex of the roof and ceiling].
Again, if there is light, it works great. If you were going outside to point the FLIR One at the roof of your house at NIGHT, I suspect you wouldn't see anything useful for an energy audit.
I'd probably save my money and get a sub $1000.00 entry level thermal camera vs the FLIR One.
The FLIR One seems more like a party trick as opposed to a truly versatile thermal device.
The very last picture is a recreation of what you see with my other "thermal device..." (A little imagination is helpful here -wink-)
One more thing about all of the attached pictures: These are the EXACT pictures taken by the FLIR ONE, they are not resized; The FLIR ONE does not take pictures at the native resolution of the iPhone (or at least save them at that resolution).
(I'm not naming the "other thermal device" specifically because posting pictures is probably a little bit of a touchy issue due to ITAR, but it works in day / night / fog / sunshine [carefully], etc.)