Snowplough on McLaren MP4-26

[Tyler]

I am very curious about the snowplough on the McLaren MP4-26 but don't really know much about it. Why are McLaren the only ones (apart from Force India, who also use it if I'm not mistaken) the only ones using it this year.
What are the advantages and disadvantages of it and why didn't they go the route of the other cars with the vanes under the nose of the car.
I'm also curious as to why McLaren decided to go down this route after Williams abandoned it after the FW31 if I'm not wrong.
Could Force India possibly be using it because of their connection to McLaren by way of a common engine supplier and is it likely to be something that we'll see next year on the MP4-27 (can't believe we're talking about the 27 already!!! - seems like just yesterday when the MP4-4 was going round the track )
I'm fascinated by this device so any info will greatly satisfy my curiosity.
Thanks

[beelsebob]

I would imagine that it's got a lot to do with the U-pod's and that it's acting a lot like a splitter.

My brain-CFD model says that the splitter's job is to provide nice clean air flow round the side of the car in the nice channels under there that most teams gouge out, by contrast, McLaren split the air somewhat higher up, and before the side pods, I can imagine that that snow plough is not only providing downforce, but causing air to spill out either side of the nose cone and straight down the U-channels.

[raymondu999]

What exactly are the benefits vs costs of each approach though? With the turning vanes like Red Bull/Ferrari vs the snowplough approach