Not a dumb question at all! They don't make the hunter anymore so you have to do some digging to figure out the differences.
Basically the Hunter frame is a lighter version of the current Tactical frame with some minor differences in how the load lifters work.
Here are some of the key differences:
-Hunter Frame is heavier than the duplex light. The difference varies depending on the size of the frame and the type of stays. When I switched from the hunter to the duplex light I think I lost about 6 oz in the my setup overall
-The duplex light is basically completely open between the shoulders, whereas the hunter frame is more "enclosed". Theoretically the duplex light breathes better due to this but honestly I haven't noticed it personally.
-The hunter frame has load lifter loops built into the frame, the duplex light does not. This means that the Hunter frame is 100% compatible with every bag Kifaru has ever made, old and new style. The duplex light only has one load lifter loop right at the top of the frame, so if you have one of the older-style of Kifaru's bags you only get load lifting capability at the top of the frame, you can't lower them. This is not a big deal at all in my opinion (I've used an old Argali for the last 2 years with the new frame), but if you have an older bag it's something to be aware of.
-Kifaru says the Duplex light is stiffer from side-to-side than the hunter frame. This means the hunter frame can "barrel" under heavy loads more than the duplex light. I never ran into this problem personally, but again, a data point.