They are essentially the same thing. I think one is a stand alone burner (AO4) and the other is a bundled system product like with the Compaq (104).
The time it takes to burn a full disc depends on the media, and its burn 'rating'. A DVD-RW can only be burned at 1x speed, which is about an hour. A DVD-R can be burned at 2x speed, which is half that. However, only certain media can be burned at 2x speed, and most of them are name brand (ie Pioneer, Verbatim, etc.), and should have the burn speed/rating on the label.