I would recommend a hotshoe flashgun with a good AF assist lamp. Provided you work within the distance limit the AF assist lamp will allow you to focus right down to total darkness!

The reason for this is that the AF assist lamp comes on briefly during focusing, then goes off. This is much less intrusive and noticeable than a video light which is constantly on! Generally the best shots to be had at a wedding happen when people don't know they are being photographed. Walking around with a big light above your head is going to make people very aware of you.

For the actual lighting I would use the flash, provided I could bounce it off something to diffuse the light. Outdoors this usually means the side a building or a canopy. This is a real advantage of the flash as a video light wont be bright enough to bounce, as spreading out over a wide area costs a lot in terms of power. Here is an example of an outdoor bounced flash portrait:

I only use direct flash as an absolute last resort, in fact I'd almost always prefer a longer exposure high ISO shot, with everything that entails.

PS If you shoot Canon there is a useful hack whereby you remove the red plastic cover that sits in front of the LEDs, increasing the brightness (the cover is replaceable if you do this carefully, I didn't!) The light still comes out red so I don't really know what the cover does.