Kakashis uses an instant offensiv jutsu, while Obito uses his Kamui more like a defense, but what he can use offensively in close combat. Kakashis kamui is faster than Obitos, but Obito can also use combo with katons with it.
But there are some aspect some people are forgetting. Obito not only is Uchiha, but also has Hashirama DNA(thanks to Madara), and it's the reason why he can use Kamui without problems. I'm sure that if he didn't had Hashirama DNA, he could not have spamm Kamui that much, so his defensiv Kamui must also take a considerable amount of chakra normally, so if we really only look at the jutsus, i think Kakashis kamui is better cuz with one kamui you can defend yourself but also warp someone by far distance instantly, while with Obitos kamui, if you can't spamm it, if you don't have Hashiramas DNA for example, just using one kamui to protect yourself by going in another dimension won't help that much and you will need close combat to warp someone.
But since Obito is a Uchiha with Hashirama DNA who can spamm his kamuis, he has a better use of it
