I am a JX-3 guy. I used to use a Millenium M60u. I compared my JX-3 setup the M60u and I do save a few lbs (with the M60u, you need to include the ratchet strap, the tree bracket, and a separate RC or TMA harness to do a fair compare). But, its not a big savings. However the JX-3 is actually more comfy than the M60u (which is a pretty comfy stand). Also, I like facing the tree for concealment and having the mobility to go around.
But if your weight conscious the JX-3 is not for you. My average walk is between 0.5 and 1.0 miles. I just look at the extra weight (vs my kestrel) as helping me burn calories during season. It sits pretty well on shoulders and hips. It really helps with longer sits big time...forget about hip pinch...try staying awake.
But, if I was going real deep all the time, then I'd definitely be using my Kestrel Flex more.