stinkypinkyI've heard great things about both bindings. From my experience the AAA's seem to be lighter and have a more traditional heel piece. The AAA's also feature a horizontal toe spring, and release from the boot well. The FKS on the other hand is a solid binding and is widely popular due to its turn table heel and insane power transmission. I've heard that the safety factor behind the FKS heel is a life saver but I have also heard that it is bullshit. If protecting your ligaments is a major factor you just might want to have a look over at KNEE Bindings. Hope this helps a little!
DON'T GET THE KNEE BINDING, OP. For starters, the bindings will force you to have a designated left and right ski, which you'll end up using one side of the edge on each ski. Second, it's very heavy (heavier than the FKS) and bulky, so it's not the best choice even if you're skiing park.
I'm also weak in my right knee but it was due to a partially torn meniscus, and I opted for the FKS 120's mainly for durability & the fact that the pivoting heel piece can release when you take a bad crash. However, the Attack's are lighter and have a small toe piece (just like the Marker Griffon's and Jester's). It's heel piece is more on the traditional size regarding bindings (like Salomon bindings).
Lastly, NS isn't the best place to get a binding. You can get a general sense of what people's preferences are and how they like the bindings, but it's best to talk to someone at your local ski shop and they'll determine the right binding for you. Hopefully this will help you out, OP.