Danny- The Ultimate Direction FKT & AK packs are very similar but I give the nod to the AK 3.0. The differences aren't that great, but here are some specifics:
I like the front pockets better on the AK. I can carry more stuff in the front with the AK vs. the FKT, which means easier access on the go. Another difference is the bottles/pockets sit a little higher on the AK vest vs. the FKT. (I don't really have a preference either way, just something to note). I do prefer the Collapsible/Flexible bottles that come w/ the AK to the Hard/Flat bottles that come w/ the Jurek FKT. I don't like the Hard Bottles & swapped them out for the Flexible Bottles that came w/ the AK vest. (The great thing about the flexible bottles is you can collapse them as you drink so you don't have to listen to your liquids sloshing around as you run. This may not be as much of an issue for hiking). On the AK, the material that sits against your body seems to breathe a little better than what is used on the FKT.
Another difference: the 2 front straps on the AK are fixed to a rail on the front of the vest that allows you to slide them up and down to adjust for fit and comfort on the fly vs. the FKT's 2 front straps that are locked in place in 10 possible slots on each side of the front of the vest. Both vest's front straps can be tightened or loosened instantly as needed but to move a strap higher or lower on FKT vest you'll need to take the pack off and insert the end of the strap into a slot either above or below where it was. As a practical matter, I don't find myself adjusting the straps up or down that often. Only if my load has varied significantly from the last time I wore the vest. Also note: I haven't had a problem on the AK with the front straps loosening up on the rail & sliding up/down on their own, but who knows if that will continue.
On the FKT, I like the "burrito pocket" on the upper left chest as a place to put your phone. It's a nice, water resistant pocket. Easy to access w/ your right hand.
The FKT vest sounds brand new, but it's really more like an update to the SJ 1.0/2.0. The SJ 3.0 is actually the brand new vest.
These are the biggest differences I noticed between the FKT & AK. They're both great vests, I just prefer the AK 3.0 overall.
I used the AK 3.0 on a self supported race in Alaska last summer (Resurrection Pass 50 miler). I carried a hydration bladder, water bottles, water filter (Sawyer Squeeze), bear spray, rain coat, long sleeve tech shirt, small bivy sack, camera, phone, about 2000 cal. of electrolyte drink (Tailwind), & food (potato chips, fritos, bean burritos, dried mangoes, nuts, chia seeds). It was filled pretty close to capacity, but the vest was rock solid. I was very pleased with its performance.