Madara wins. Obito and Kakashi would normally be an impossible to beat duo, but if either of them teleport Madara to Kamui they lose since Limbo will allow the latter to attack from both dimensions, so if they phase they still get hit. If they know of Limbo beforehand then they stand a far better chance fighting against him in one dimension with Obito against Madara and Kakashi struggling with Limbo, being unable to see them (note that the shadows have the force to knock around Tailed Beasts, even before attaining the Six Paths Sage Mode). Obito and Madara clad in their Susano'o would probably be in Obito's favor due to Kamui until the shadows finish Kakashi off.
