One thing you may want to check into is if these racks will allow you to use your rear hatch when the rack is on the car.
We have a Subaru wagon and needed to still be able to use the rear hatch with the rack mounted. I don't think the ATOC will allow you to use your hatch if the rack extends past the end of the car. The Thule has a removeable rear section and the Yakima mounts the Tandem at the rear crank area so there is no rear wheel tray like the others.
We opted for the Rocky Mounts Tandem R4
http://www.rockymounts.com/TandemMount_R4_p/0512.htm
it has a retractable rear section so it can be moved in and used as a single bike mount or out for a tandem. All it takes is a couple of turns on a large wing nut then the rear section will move in or out as needed. If we use the tandem and need to use the hatch area we just take the bike off first before using the hatch and when putting the bike back on the car after the ride the bike goes back on the car last. We don't have to deal with the loose rear section like the Thule has.
It's excellent quality with beautiful welds and has a pivoting head mount. The only thing I don't like is it's painted silver instead of black.