I haven't had time to see the shootout yet, but it's logical that larger sensors have some advantages, at least as long as the photosites are larger. However, from a practical point of view, the GH1/2 offer a lot more than lower price and the possibility to mount more or less any lens.
To start with, they have a viewfinder. Although the Zacuto viewfinder and similar solutions work ok, they don't beat a proper viewfinder, and with the Panasonic, this comes in combination with an articulated LCD.
The camera body is much smaller and lighter, and you can easily fit 2 x GH2 within the weight and size of a 5DII. That comparison even holds for the price, and if really small is needed, it's easy to add a GF2. There is no GF2 in the full frame world.
Lenses are much smaller, particularly when it comes to telephoto lenses, but the same goes for WA lenses. I have on several occasions been shooting together with photographers using a D3s with Nikkor 14-24mm. The size difference is so enormous that it looks silly.
For people working in a studio or with a large crew, this isn't very important, but for small crews on the go, or one-man-shows like myself, it's of paramount importance. I can carry two GH bodies and 6 lenses in a small Kata Kata DR-467i backpack that also has space for 3-4 days of clothing, a fluid head and a small tripod on the outside.
I don't know how dramatic the quality difference is, but I do know that there are many places where I would never carry full frame gear, simply because it's to bulky and too heavy. In addition the difference in reaction you get between pointing a D3s with a 200mm lens at people compared to a GH1 with the OM 100mm is enormous. People simply act differently when a big camera and lens is pointed towards them, and that affects the real qualities of the video.
So, the best isn't always the best, and although we are discussing technical quality on this thread, it's important to remember that the technology has to work within a context. Horse for courses and so on.