I see the IR hunters come with the different lens, is the 35mm better than the 19mm?
I do realize the on regular scopes, the bigger lets in more light, but thermal? Or is it just larger FOV?
Just a noob not understanding.
Also, is the Larue QD a good mount for take off/on repeatability?

LWIR is "light" and the lenses work on similar optical principles as their visible-light siblings, but generally speaking the "bigger" the lens the less FOV and more "magnification." 19mm will have less "reach" but more FOV.

Hard to go wrong with LaRue on anything.

it also gets complicated because there are different sizes of detector (focal plane array or the thermal detector )behind the lens so a certain size lens could give a certain magnification or fov.on one scope but a different magnification on another with a smaller or larger detector  or one with more pixels etc.

Well, I finally sold the last rifle to get the cash for one of the IR Hunters in the group buy, now it's time to fish or cut bait.
A few more questions tho.
I realize that the more magnification, the worse it breaks down the target, but what power are these capable of, either I can't read or am going blind.
Can these be used during the daylight in case the hogs come out early?
Which one would you choose and why?

The latest-gen IR Hunter seems to be the one to beat, and the price is fantastic. I wouldn't get less than a 35mm objective, and 320px is usually sufficient, but 640px is better if you can swing it. The added resolution won't appreciably increase detection range but it will increase ID range. You can use thermal at any time, day or night, which is a distinct advantage over i^2 (NV) technology.