I believe you guys misunderstand his question.
You're right, ha, it makes a lot more sense to me now (in the context of video card fans). I feel silly.
Both have advantages, but generally, the ones that expel heat into the case cool the card better, but you should have good air flow in the case to prevent heating up other components.
They (axial fans) also tend to be a bit quieter than the other (centrifugal) type. This is the reason board partners like Gigabyte employ coolers like their Windforce (or MSI's Twin Frozr) as opposed to the reference cooler (which is often, but not always, a centrifugal cooler).