The payload of h-6k is described as 12 tons( 15 by some). While that of jh 7 is at 9 tons. Can somebody give an idea as to why a plane thrice as bigger than the other only carries 50% more payload?. ( i'm considering range?)
Thrust-to-weight ratio is one reason. The JH-7 has afterburners and the H-6K does not. Another reason might be a less optimized airframe with less body/wing lift.
Regardless of that they were both interim designs. The JH-7, it seems, will be replaced with the J-16 which has better specs in all regards as far as I can see, the H-6K is just an intermediate platform until the H-20 becomes available. Still both of them are vast improvements over their predecessors (Q-5 and H-6).