Okay, I know I may catch allot of heat (hell) here for posting my own personal opinions as a result of my use of thermals over the years, so here is my knowledgeable learned advice for thermal beginners (NOT experts) to rip into me over....lol
Either an RS32 or RS64 with 35mm lens would suffice for 95% of all hunting situations I find myself in with 5.56mm and 7.62mm out to 225 yards and placing an accurate lethal shot.
After a couple of years of thermal scope experience what I have learned is that I WANT MAX FOV, being out in the woods at night under all kinds of weather conditions, often times not knowing or familiar with the terrain and environment of where I am at from previous visits during daylight, max FOV is a major asset.
I find that FOV is absolutely a top notch requirement for me to hunt. Ease of use of the ergonomic controls is also a huge asset in the dark when seconds count. Follow up moving shots also require wide FOV and a nice open uncluttered reticule to shoot off.
I also like a 0.5X or 1.0X ability as anything magnified is just for zooming in at, most of the time it is being used in the lowest power possible.
It is kinda like when I first got my FLIR T-70 thermal:
I shot all these pigs alone by myself at night in about 20 seconds with a 7.62mm & T-70 (there were two more bodies I recovered the next day too for a total of 7 confirmed and recovered kills in 20 seconds):
All the other supposed "experts" were making statements to me like:
"Oh, that's not powerful enough, you need larger than a 35mm lens, get a 60-100mm lens instead. BS, it blows away everything I ever shoot at.
That T-70 is only 640 resolution in the 0.5X mode, in 1X unity mode it is 320 resolution. BS, I absolutely LOVE the 0.5X mode, wish more thermals were marketed with it, everyone that uses it also comments on how much they like it too.
The mil-spec L3 LWTS is so much better than the mil-spec FLIR T-70. DOH, it does not have 0.5X mode and their availability/service is next to nil, FLIR has absolute killer service and accessibility to their excellent service network.
Basically, an LS-64 hand held thermal scanner does 95% of everything I ever need to do, a RS64-35mm thermal rifle scope will also.
A PS-32 hand scanner also will do 90% of everything I ever need to do, and an RS32-35mm thermal rifle scope is even better than that!
60mm lenses are for long range 300+ yard shots at night, which is not happening in the swamps and jungles I hunt in, nor am I capable of making a safe effective 300 yard shot at night anyhow in most situations.
35mm lenses are great for extended short range shots at night out 225+ yards, which covers most of what I do.
19mm lenses are great for short range 100-125 yard shots, which is plenty for allot of predator hunting or hog hunting situations too.
Both the 320 and 640 cores perform real well, the 640 performs better at higher magnifications and is a tad clearer, but out 225 yards like I said, they both perform real well.