To me it looks more and more like the focus of the investigation and certainly the media is on AOA. They are making a big deal out of the fact that a single AOA could trigger MCAS activation.
I've thought about this and I'm coming to the conclusion that there are valid reasons for either single or both activation. It's a choice the manufacturer makes and there are plus/minus considerations no matter how you wire it.
If all sensors are working correctly, either method works fine. AOA gets high and the first sensor to "see" AOA >1.00 triggers the stickshaker/stall barrier/MCAS/whatever system the aircraft has. This would be the FAA certified G-550 method. Or, in a two sensor method, AOA gets high and BOTH sensors "see" AOA > 1.00 and together they trigger the stickshaker/stall barrier/MCAS/whatever system the aircraft has. This would be the JAA certified G-550 method.
Now think about a situation where just ONE AOA sensor goes bad. It can fail either way, that is it can FAIL to sense high AOA when the aircraft approaches a stall or it can FAIL by sensing high AOA when the AOA is essentially normal for that phase of flight.
In the case of a single sensor trigger (FAA G-550), if this bad single sensor FAILS to sense high AOA, the other good sensor will still trigger stall alert/protection. That's a good thing.
OTOH, if a bad single sensor FAILS and senses high AOA incorrectly, it triggers a stall alert/warning that should be handled by the flight crew using the abnormal procedure that already exists and that they should be able to perform without reference to a checklist. So, no valid reason to crash the airplane over an incorrect reading from a single bad AOA vane.
Now, in the case of a dual (BOTH AOA vanes) sensor trigger (JAA G-550), if this bad single sensor FAILS to sense high AOA, the other good sensor will NOT trigger stall alert/protection. I'm not so sure that's a good thing. If you are stalling the jet and one AOA sees the stall and the other does not...no stall alert/protection.
OTOH, in a dual trigger system if a bad single sensor FAILS and senses high AOA incorrectly, it will not trigger a stall alert/warning. This basically avoids a nuisance stall alert/protection event. That's a good thing but is it critical? There are established procedures for this situation in every jet I ever flew.
I guess each of us has to decide if a dual system is better or worse than single trigger.
I see it kind of like this. Consider a situation where one of your AOA vanes has failed or is inaccurate for whatever reason.
A single trigger system will likely warn you every time if you are approaching a stalled condition; it will also possibly give you false warnings.
A dual trigger system will likely not give you false warnings but may fail to warn you if you are approaching a stalled condition.
What do y'all think?