Another asspull from Kishi.
Jesus a thread was ,ade about this already.. it just means that Madara is a better jin and has better control meaning he's good enough as a Jin to use Kamui. Has nothing to do with Kamui skill as that hasn't been implied from what I see currently.
Or we cam just call it a plot hole unless Kishi explains it in the next chapter.
aaa OK , i was thinking he was not able to switcht the demisions cuz the Juubi is to big . =D