I haven't even seen Kabuto's yet but i'm sure when I do it'll become my favourite. Kakashi's is my favourite for now, it was just a genuinely well-told story.
Kakashi and Obito's gaidens are just a part of the same back story, right? I mean, Obito's continues right where Kakashi's left off, and we're about to see Kakashi again anyway. And to hate for a moment, Kabuto's story was unwanted on my part. And kinda dull.