What happens now when you want to select manual thrust? If the levers are sitting at say, idle but you want to maintain or increase thrust what do you need to do to match them?
In the A380 the levers can move over a normal range from idle to max. But there are a couple of gated positions at the extreme extension. TO/GA, MCT/FLEX, and CLB.
Normally, you take off in TO/GA or MCT/FLEX. Shortly after take off, you pull the levers back to the CLB detent, and they'll stay there, not moving, until you land (which is what that 'RETARD' call is there to remind you of). Autothrust is not active in TO/GA, and almost always inactive in MCT/FLEX. The exception for MCT is if you have an engine shut down, in which case the levers will be positioned to MCT, and the auto thrust will remain active.
The button on either side of the thrust levers is called the 'instinctive disconnect switch'...but, don't press it instinctively. As the levers are normally at the CLB detent, pressing that switch will disengage the auto thrust, and then give you CLIMB (which is where the levers are). You have to pull the levers back, to approximately match the selected and actual power, before pressing that button. Pulling the levers out of CLB with the auto thrust engaged has the effect of limiting the A/Ts authority...and has no use in day to day ops.
In the Boeings, the levers are moved by an auto thrust servo system, so that the lever position always matches the commanded power. If you disconnect the auto thrust, nothing happens, because the levers and actual power are always matched.
Overall, I think the Boeing is better system, especially as it doesn't have the effect of disconnecting the pilots from thrust lever position and motion, something they'll need if they have to revert to manual thrust.
But....
In an Airbus, you activate go around mode by pushing the levers all the way forward to the TO/GA gate. In Boeing by pushing the 'go-around' switch. As we've seen recently, this can lead to a pilot group that pushes the button but doesn't follow up by pushing the levers up. There's video of a 777 in Munich, and the accident at Dubai, in which this plays a part.
So, the perfect thrust lever system would be a mix of the two.