A substantial difference between them, is automation had totally checked out in the 447 case, whereas in the MAX cases automation took action contrary to reality.
I let the engineers argue over redundancy. As a pilot I think it's a factor, but far less so than the pilots being denied knowing their airplane.
447 pilots had not undertaken any in-flight training, at high altitude, for the “vol avec IAS douteuse” procedure or on manual aeroplane handling; while the MAX pilots had no training expressly on MCAS upset so they could experience the exact consequences of ensuing mistrim, the difficulty of solving that mistrim at low altitude, and the aggressiveness of MCAS in any subsequent nose down. MAX pilots are additionally denied knowing about the true pitch up tendency in high angles of attack without the benefit of MCAS (either it wrongly thinks AOA is OK, or stab trim is cutout).
The Ethiopian Airlines pilots had the situation progressing toward stability. They had (apparently) re-enabled electric trim to give them enough authority to reset the trim, and had a sane attitude. But then within seconds they lost their chance as MCAS took incredibly aggressive action that put them in an unrecoverable 40 degree nose down attitude.
There really is no substitute for training. I don't accept that the "fix" for the MAX is a software update alone. Simulators must be capable of showing various kinds of MCAS working, not working, and perturbed (erroneous sensor input) cases, at various phases of flight. All the excuses to avoid training are bullshit.