I have the 19A and also an HD 50S Apex, which has the OLED screen. The OLED screen is better, but alone is not enough of a reason to choose the 38S over the 19A, IMO. I reach a different conclusion with a scope rather than a spotter, fwiw.
Detecting fox, coyotes, and any larger critter at 300-400yds is no problem with the 19A. Smaller critter too, if they are not partially obscured. Much longer ranges are good too for the larger critters. Pulsar significantly understates actual, in-the-field detection range of the 19A.
The terrain where you hunt might be a better determining factor in your choice. The terrain where I hunt ranges from small tight areas to more open terrain where the next tree line might be half, 3/4 mile or more away. I love the 19A in the tighter areas where FOV is king, I wish I had the 38A or S when I'm hunting the more open areas. I primarily predator hunt and picking partially obscured critters out of a tree line where you are picking the critter's heat return from the return from residual heat in tree trunks and other brush would be easier with the 38S because of the bigger lens, greater magnification and better screen. With the 1x native magnification and LCD screen of the 19A, distant returns right at the tree line can be hard to pick out of the clutter. I hunt with a bud who used to use an MTM 320 unit, which was better than my 19A (and ought to be based on cost) but not by that much, when he upgraded to a 1x 640 OLED spotter the performance differences became really apparent with the ability to differentiate critters at/in the treeline most significant. I think the 38S would make up a lot of the ground compared to his spotter in those circumstances.
Welcome to LSB's. Great bunch of guys here who are very helpful and like to share info and opinions without the vitriol so common on some other sites.
JPK