yeah, i agree, with my mouth alone Goku can reach tier 0 =))
So now i give my vote to Chou Goku, GT Goku with Dragon Fist can destroy Omega, but it is because Omega is caught off guard because he think Goku still blind and Goku overlap a Dragon Fist on top of a Kamehameha Wave, and even when the Dragon Fist connect, it take a good deal amount of times for Goku to penetrate Omega body, Omega still withstand it for awhile. In this scenario GT Goku is not blind, and even then Goku is Goku, he can being caught off guard by others, i doubt he being fool by himself a same person, they have the same chain of thought and skills, so GT Goku outsmart or outskills Chou Goku is non-existent.
On the otherhand, UI Goku is above baseline 3-A, that mean his casual attack is 3-A atleast, while GT Goku need to prepare for a Dragon Fist at full power is a disavantage and even the hit is connect to UI Goku it is still a tie because UI Goku is casually 3-A, any kind of his strike will cancel out Dragon Fist; fighting skill and tactical is pointless because UI Goku is totally Instinctive Reaction, and because of that his overall speed is better especially reaction speed allow him to defence and counter his opponent attack more effiency.
This is my explaination for my opinion that Chou Goku win GT Goku, sorry i'm not good with English
Edit: Wait, could GT Goku sense Chou Goku, i mean Chou Goku have God Ki and people who is not God or not being trained specially to sense God Ki unable to sense this Ki???