Ted has explained things well, The FL and HT both used Abbe Koenig prism systems and are very bright.
The SF is the highest Victory model, it uses SP prisms, and is similar to the Swaro. EL only better.
I own both so this is from experience over several years.
The SF has a wider FOV, has a very nice balance due to its design with the balance to the
ocular side, and its focuser is as smooth as butter, better than the Swarovision.
I have owned the FL 8x42, a very nice binocular, the HT is similar, but now discontinued.
The SF is at the top of the heap right now.
If looking at a new 8x42, be sure to check out the Victory SF. I have the 10x42, and it is very nice.
