Double bladder wings have declined in popularity because many divers concluded that they aren't any safer than single-bladder wings. Compared to a bag, the upside is that you can finish the dive with a normal amount of buoyancy and trim control rather than having to fuss with something that's an awkward shape and that is tending to pull you into an awkward orientation.
Some divers use two wings, instead of one wing with two bladders. Regardless, there are two possible ways to configure the two bladders. Each poses problems.
Method one. Each wing's power inflator is connected to an air supply
The problem here is that it is difficult to diagnose problems with a power inflator that is dribbling air into the wing. It is possible to have the secondary wing inflate slowly over the course of the dive and not realize that there is a problem until it is impossible to control ascent. Problems venting the wing must be solved quickly and the automatic (and usually correct) response is to try to exhaust trapped air from the primary wing. There is some added risk of a runaway ascent with this configuration that must be factored in when evaluating the safety benefit of being able to control a runaway descent due to a wing rupture.
Method two. Secondary wing power inflator isn't connected
The problem then is that it potentially takes longer to connect the power inflator to the secondary wing (or to inflate the wing orally) than it would to deploy a lift bag from a pocket or other reasonably accessible location. The usual approach is to inflate orally, but when a good deal of the wing capacity is in fact needed, this takes time and concentration. Once a lift bag starts to fill from a regulator that has the purge button depressed, it fills quickly.