Just my thoughts - think about where you're going to be using thermal and for what. What you can use effectively in a barn will be a lot cheaper/lower spec than what would be useful in large open areas
All thermal has some of the same limitations -
if it's misty or has been raining for a while, you will still spot quarry due to the heat difference - what you may not see is any surrounding detail as the temperature of everything else is the same - not really an issue with a spotter, but with a sight where you need to identify your surroundings, what's behind your target and range it can be tricky
My first thermal was/is a HikMicro LC06 the smallest, cheapest Hik available.
Pros
very wide field of view - effectively 1 - 1 with your eye so you can scan a large area quickly
lens is so small no focus to worry about
does what it says - it spots things well
Cons
not very sharp picture - even under ideal conditions appears grainy
small sensor
at most distances (I've detected rabbits at 100m with it) identification is more a case of knowing how different animals move, especially on smaller ones - i.e. until they move a hedgehog and a rabbit squatted down will both look similar - a glowing blob
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rat at 8yds - damp conditions
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squirrels at ~50yds
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rabbits at 20 - 30yds
Last year I purchased a HikMicro Thunder 2.0 19mm sight just after launch
this was purchased mainly to help deal with very skittish rats in the garden - with the 6mm spotter I'd see a rat, raise the rifle with NV and it 50% of the time it was gone, wait 10 min on the NV, no show back to thermal and it would come back out, pick up rifle again....rinse and repeat, very frustrating.
Much sharper picture and range but considerably smaller field of view (about 2.5x),, but back to scanning and shooting with a rifle (it does make a very good spotter if not on the rifle) and a more sensitive sensor - you can see heat reflecting off animals and where they've been sat. Need to focus for sharp picture
you can see the heat of the approaching rat and it reflecting in this video before it appears
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rat at the same 8yds - similar conditions - misty and damp
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same range - better conditions
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rabbits 70 -80yds - not quite focused (and not on rifle)
And finally at the weekend I picked up a second hand Guide TrackIR 50mm spotter - it's a couple of years older than the Hiks with a larger but slightly less sensitive sensor - not had chance to do much yet. A smaller again field of view and again need to focus - quick comparison between the Hik 19mm and it both at 25yds - £400 2nd hand
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Hik
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Guide
One thing to bear in mind is that the output video never looks as good/sharp as what you see through the scope/spotter.
So what would I change ? weirdly probably the Hik 19mm scope - but that would only be to a model that had a built in LRF (with or without BC) - it's plenty for sub 12 and rimmie but with sub 12 where ranging is all important, the flat digital screen has the same issues as digital NV scopes in the dark (you are looking at flat screen at your aim point with few reference points between you and target) compounded with thermal's limitations based on conditions. If I'd bought it as a spotter I probably wouldn't have picked up the Guide (although at the price it was a bargain)
One thing though I won't get rid of is the little 6mm, it's light and I can scan way quicker without having to worry about focusing - and if you're shooting with NV all you need to know is where the little buggers are