For an inflatable to be considered a PFD it must be worn. If it is not being worn it is not even considered a PFD to count for any one aboard.
As far as it not turning you over if unconcious, that is correct. However, most of the PFDs carried aboard a private vessel also will not do that, and you will not even be wearing the ones that are typically carried aboard. They will be stowed away under a seat somewhere.
I do agree that the self inflatables would be the better of the two.