RIght now, the Pulars are the "budget" solution running from about $2.5k up to just under $5k for hunting usable thermals.
The Trijicons are the "high end" (under $10k) solutions.
The Patrol is very flexible, it does just about everything, not as well as some of the larger options, but flexible is flexible. On your head or in your hand as a thermal spotter. On the weapon as a scope. And with a 3x magnifier you get more distance for spotting.
Hard to argue against one of the 300 patrols.
Probably the best thermal image we can buy under $10k is the larger patrol 250xr with the 60mm lens.
THen there is the REAP and the SNIPE ... all four of those are the "joystick" trijicons. Smaller and lilghter than their "IR_Hunter" brothers. The REAP is the 35mm joystick housing designed for spotting or weapon mounting. The SNIPE has a collimating lens on back, instead of a diopter and is designed as a clipon.
The IR-Hunters are larger and heavier and are designed for weapons mounting ... they are the "turret housing" group.
Both groups have 19mm, 35mm and 60mm focal length versions. The longer the focal length, the lens field of view you have, but the more magnification you have. Basically you can see more detail at longer distance with the longer focal length lenses at the expense of having a smaller field of view.
So as to the focal length, it really depends on your terrain. The more open your terrain, the more you would lean towards the longer focal length. The closer your terrain the more you would lean towards the shorter focal length.
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I have had a 35mm Hunter for 2 years and it has served me well in my home terrain which is woods, hills and creeks. I've also had a SNIPE, which is also 35mm.
The 35mm focal length is a good compromise, I can PID hogs at 1200yds and I have 12 degrees of FOV for my coop defense along a wooded creek where most spotting and shooting is inside 100yds.
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If you want to dive in maybe try an ir-hunter 35mm or a REAP 35mm since they are the best balance.
If you want to proceed more cautiously, try a Pulsar Trail XP50 for 1-2 years first and save a a few k.
They all get the job done.