OK, for thermal riflescopes I have an ATN 640, 5X, IR Defense MKII, IR Patrol (used as a helmet mounted monocular) and Pulsar XD50A. (I also have an ATN OTS-X E370, 6X thermal monocular and Pulsar HD38 thermal monocular). The only difference between the 50 and 50A that I know of is the screen. The 50 has OLED and the 50A has LCD. It is hard to come off a grand for an OLED screen, though there is a huge difference in sight image quality. You can definitely pick up a 50A for well under 4 grand (closer to 3 if you shop around) and might get a 50 for close to 4 grand.
When you are use to 640 cores, it is a bit hard to adjust back to 320 or 388 cores at times. Just the same, I am very happy with the XD50A's bang for the buck. It is simple to operate and has some nice features. I like the option of choosing manual, semi-auto and auto NUCing. I use semi because I don't want it calibrating at the point of trigger pull. I wish the much more expensive ATN, MKII and IR Patrol that I own had this feature. I also like color reticles and the ability to adjust their brightness.
Recording... I don't know if you record or not, but that is important to me. Both the ATN and IR Defense require you to turn the "video out" on each time you turn the scope on. The Pulsar's "video out" is active all the time. That is one less thing to have to think about. If you record, you may have noticed something else, the IR Defense recording looks better in 2X than 1X which defeats the 640 core to some degree and narrows your field of view.
PiP... The Pulsar has Picture in Picture. No one else has that. It is a very cool feature that gives you a small magnified window of the crosshairs that helps you place the shot much more accurately.
One Shot Zero... Works very well. I had no issues sighting the weapon in and it gives you numbers to dial back in should you move the scope from weapon to weapon (though I can never trust that without checking it, may just be me). The new MKIII has the ability to retain the numbers for sight in, but the MKII and IR Patrol do not.
The menu system works very well and is intuitive...
Here is a video I did with my XD50A. It is boring unless you have an interest in whether bobcats will eat corn or not. Lol... I think the video is better than what I get off my MKII or IR Patrol:
Now, do not expect the beautiful sight image you see through the MKII on the Pulsar. It isn't there. I am always awestruck by both the MKII and IR Patrol. On the flip side, for roughly half the money, the Pulsar is definitely feature packed and great for either a starter scope or backup. I would definitely buy it again.