If you frame it that way, I think B is more believable, because it accounts for the television/monitor, the controller, and the general fact that the player doesn't experience any of the physical repercussions of his/her actions. If B was what was really happening, then of course there would be camera effects, and of course I would need a monitor to view the actions from the camera, and of course I would need a controller. If A was really happening, then why would I need any of those things? So A is a bigger jump to immersion.