Can you test ride them? I have a Mk3 and another (Norco) FSR bike. My GF has a faux bar (like Boardman) bike. The DW link blows the others out of the water for climbing and descending, even with just a Float and no Pro Pedal adjustment, but as said above, there probably is very little warranty.
The IH is probably by far the best frame, but what is the rest of the build, and do you want to buy a bike to upgrade around? Personally I'm tempted on swapping my Norco for a bargain Six Point… This said I weigh 8st so I'm unlikely to snap it and am not too worried about warranty.
If the Anthem has the Maestro system (I know nothing about Giants), which I believe is a similar style to DW link, then maybe get that?