The Saker will be the strongest because of its baffle design, it has an interchangeable rear end for switching out mounting options, and it has a removable end cap for adding a flash hider or a 5.56 endcap. The SDN-6 is also very strong, and it's the same size, weight and loudness as the Saker, but it only fits on one type of mount (the AAC 51T mount) and doesn't have the modular options of the Saker. And the 762SD is a re-release of the older AAC can that was replaced by the SDN-6; it's longer, heavier, and not as durable as the SDN-6. But because it's 3" longer it's going to be quieter.
I say get the Saker if you like the different mounting options (they currently make 5 different MAAD mounts with more to come), or if you are going to shoot it a lot on an SBR and/or a 5.56 rifle (the baffle design is slightly stronger than the SDN-6 and you can put the 5.56 endcap on it to make it quieter with 5.56). But the SDN-6 is a great can that performs very well and is usually cheaper than the Saker is (I have one and love it). Or get the 762SD if you don't mind the extra length, you're not planning to shoot a lot of rapid-fire mag dumps, and you're not using it on an SBR; it's quieter than the other two and a lot cheaper.
Also, keep in mind that AAC has extended their "Damn the Man" $200 store-credit rebate until the end of the year; for every AAC rifle or silencer you buy you get $200 to spend at their online store, which is great if you'll need more mounts.