My own opinion is an AAV vs. busting up a slab? No brainer. Use an AAV.
So, AAV's "fail"? Oh, my. Bring a $5 bill to a home center and walk home with a new one, in the case that they do fail.
The "Carson Dunlap" diagram in reply #5 isn't quite right. It says, "System at rest: sealing mechanism is closed when there is positive pressure from gases"...Well, the sealing mechanism is held closed by a spring, REGARDLESS of the gases. It's nothing but a check valve for air, and it flows in one direction (INTO the piping system). Because it is held sealed by a spring there is a "cracking pressure" that is required to open it; the cracking pressure is the pressure differential between the input side and the output side.
Because it is meant for air, not solid waste, sure if there is backpressure from sewage it may very well spill out. If that's the case it may be installed wrong; there are right ways and wrong ways to install them.
Now, if you can adequately install a hard vent pipe, without busting slabs, opening walls, or other highly invasive means or if it is required absolutely, then do it.