Guy uses a Hirudora right at Kakashi

[hokutoshinken]

He kamui it, then send it back to Gai from the other dimension or kage bunshin, doton, kamui himself etc...

This.
I'd add Taiju kage bunshin and Shunshin jutsu

 

[paratise]

He can not kamui something at that size and force; Hirodura comes with great speed and force, not only size; would he even be able to react to make a substition or another escaping tech?

 

[garas56]

Logic says
Kakashi>Guy
Guy>Itachi
Itachi>Kakashi
The end of talks.....

 

[Takos]

He cant Kamui Hirudora at all, it is just air pressure ..... You can't Kamui air ..... XD

Why not? Obito kamuied it in reverse to make wind and empower his katon.

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Your argument is invalid.

 

[illidanson]

7 gates Guy > MS Kakashi

However it takes time to open 7 gates, Kakashi could Kamui him in the meantime. All in all i'd say they're about equal, however Kakashi has more potential as his Kamui is one of the strongest jutsus in the series.