I've tried both the Thule G6 and the Atera Strada. The nice things about the Strada are the fact that it slides, and the fact that the frame is triangular rather than square so it's much easier to get to the boot. Given that the reason I bought the rack was the arrival of pdw jr, the ability to get the sprog chariot in and out of the boot easily with the bikes still on was quite important.
The Strada does have one major flaw, which is that you can't easily swap the order of the arms, which can made loading the bikes very difficult. If you're always going to be carrying the same bikes, this might not be such a serious problem, but I could tell it was going to drive me mad so I ended up throwing even more money at the problem and getting the Strada Evo.
If you're looking at the Atera carriers for a car with a big tail gate, it's worth bearing in mind that the 3 bike carriers slide further away than the 2 bike ones.