Hi J. The difference is really qualitative Vs quantitative data, and what you need. For the later, you may need to have actual temp value of an object of interest. Say you are inspected a utility pole transformer, you need to know more than just that it has a higher heat signature in comparison to the rest of the background. you may need to know if it is 80 degrees or is it 135 degrees.
A performance sensor will have actual pixel temperature values in the center 40% of the image. A Radiometric holds an actual temp value for every pixel in the image.
In my opinion, for what you are planning on using it for you would not see any added value in a Radiometric sensor Vs performance Sensor. Just 30% more in the price. You will definitely see a major difference in quality between a 336x256 and a 640x512. A 640 is going to have almost 4Xs the pixels as a 336. More pixels, better quality image, easier to spot object of interest. I would also say, you definitely need 30Hz in either sensor if you are going to be moving (and Searching) as compared to studying a stationary object. Slower screen refresh rate is difficult for Search and Rescue.
If you can wait, buy a used one from someone on one of these forums. (Caveat emptor). If not, shop around for dealers. Some good ones on this forum. They are all similar in price. They are not allowed to discount, but if it is an "open Box" sale, they can. So, find someone that has an open box. If money is no object, my recommendation would be a 640 XT2. Having a Thermal Sendor and RGB side by side for SnR is the best of both worlds. Need to have an MSeries drone for the XT2.
