Advice on thermal scope purchase.

Looking to purchase thermal scope. Current setup sightmark photon 3.5.on ar-15. Have pulsar HD38A monocular for spotting. Hunt mostly open fields and pastures up to 500 yards in length. Mostly spot and stalk to within 40 to 90 yds then shoot. Would like to have capability to make up to 200 yard shot if opportunity arises. Budget is up to 4000 will probably wait to at least black Friday sales purchase. New upper in 6.8 spc ordered for this. Currently looking at Armasight Zeus 3x 336x256 60 hz......
Pulsar Apex XD38A.......Pulsar Apex XD50A... I can operate complicated devices if need be but the simpler the better.

Why I Choose Pulsar Apex 50a

I've owned both you mentioned and it's a toss up between them. Pulsar has a slightly better image and better controls while the Zeus has a much more robust housing and a better mount. Also the Zeus is more compact and better ergonomics. Pulsar is somewhat ackward. Of those two I think I prefer the Zeus by a slight margin. That said if I were you I would look into a used 640 res unit maybe just slightly more than 4K. Once you look through 640 you won't be interested in a lesser resolution. I currently run a Zeus pro 50mm 640 and it's the cats meow but you could get into a used Zeus standard or a Thor (non HD line) for around your max budget. Stay away from the new Thor HD models from what I hear.