I have experience observing big game, livestock and humans at night with Gen III intensified and thermal sights/cameras. I definitely prefer thermal over intensified.
I've used the FLIR Scout TS and it has a "feature" I don't like. The sky is cold at night. When the skyline drops into the field of view, the system auto gains and causes the terrain to look warm, which masks the presence of warm subjects. To prevent this auto gain process, you have to keep sky out of the field of view, which is difficult in the mountains because the skyline is not flat.
I spoke to a FLIR salesman at the SHOT Show who acknowledged the issue and told me I should use a different model. You should talk to FLIR about this issue.