@Takos No. Stop making arguments on your own. According to Kakashi himself, Obito's S/T jutsu is better than Minato's FTG. Has he ever ventured that about himself?
First of all, he hasn't stated that about his own Kamui, but he also never said his Kamui was inferior to FTG.
And besides, I said that his Kamui is better than Obito's in
some aspects, not that it was better overall. I believe that apart from lower chakra consumption of Obito's version (which might be related to Hashi's DNA and not the technique itself), their kamui are about equal or almost equal - just different.
Obito is tiers above Kakashi and the only reason he would lose, is because of the Shonen constraints, as only a few chapters back before Kurama didn't aid his unassuming ass, he, Naruto, and Gai were completely at his mercy.
I won't really argue much about it here, but you also need to keep in mind that they had minimal information regarding Obito and his techniques which made it much harder for them. Only after Kakashi's cracked it did they start gaining some ground. What's more, Naruto, Guy, Kakashi and Guy alike have been fighting since the beginning of the war with no or minimum rest, while Obito started in the middle of the second day.
Mastered? Nothing but a baseless argument as Itachi's statement still holds so does the manga evidence in regrads to KG use on any front. Obito's use of Rinnegan was better than Nagato as well, just because of the evolution aspects of Rinnegan that has to evolve from Sharingan.
Baseless argument? Kakashi is the only non-Uchiha who managed to awaken MS. And that's not all, he is tied with two Uchiha (Obito and Itachi) for being the youngest person ever to awaken MS. Even in Part II when Kakashi implied to Itachi that he has MS, Itachi almost couldn't believe it. All this speaks for Kakashi's mastery of the Sharingan.
As for your statement that Obito handles Rinnegan better than Nagato... just no. It's simply wrong. Apart from using 6 paths and supposedly being able to use Rinne Tensei, he hasn't shown any Rinnegan abilities. He didn't even absorb Naruto's Rasengan that was coming to his face.
The only reason he has Kamui is because of Obito.
Of course, but does it immediately mean he could not master it?
He has not shown any complex chakra detection abilities or extremely fast movement detectiobn at the level of 3T which Uchihas possessed.
But he was still able to fool two full-fledged Uchiha with his perfect timing.
1. Itachi himself admitted Kakashi's timing was perfect, due to which he didn't notice Kakashi creating a kage bunshin.
2. He kamuied Naruto's clone in front of Obito with such precision that Obito believed the clone was destroyed instead and kamui missed.
