If anyone says MS Obito>MS Itachi, then they do seem like an Obito fanboy tbh. At least the ones saying MS Itachi>MS Obito can back it up somewhat.
-Itachi's counter for Obito's kamui is any surprise attack. Obito had to use Izanagi on Itachi's amaterasu activation, he ended up losing an eye. I don't know if he could afford to lose an eye in a battle against Itachi. He has also lost an eye to Konan for using Izanagi during her trap. He lost his arm twice once to Minato and once to Torune. So much for kamui hype. You can also attack Obito for longer than 5 minutes, considering that is the time limit that he can stayed phased out for.
-In the RTN movie, Itachi said that even though Obito had kamui, there was still a way to hurt him and kill him. Kishimoto wrote the entire script for the movie.
-What real counter does Obito have to Itachi's genjutsu? Not looking into his eyes is not a valid argument, considering that Itachi has non-ocular genjutsu as well. (Same logic as Obito's fanboy logic with kamui.)
-When Itachi stated that Madara was his mentor during his fight with Sasuke, that was a lie. He wanted Sasuke to awaken MS, then take his eyes and gain EMS in order to stop the blindness, then go after Tobi and kill him so he could be deemed even more of a hero. He had to give a reason as to how he knew about Tobi and Sasuke did ask who else was with him on the night of the massacre. So Itachi lied. Kishimoto also made a point of having characters such as Kabuto and Obito state that everything Itachi said was a lie. If anything, Itachi learned from reading tablets himself and some basics from Fugaku/Shisui/theAcademy. This claim that Obito trained Itachi is also thrown out the window considering that nothing in Itachi's moveset is like Obito's, he only knew Obito for 7 years and had already mastered his sharingan prior to then, and Obito admitted to trying to stay out of Itachi's presence and hiding secrets from him, like Izanagi.
-The claim that MS Itachi is weaker than MS Obito just because he did not kill him does not hold very true either. Itachi stayed in Akatsuki for 7 years and the manga confirmed towards the end of pt1 that the Akatsuki had not all met together since the day Oro left, which was the same day Itachi joined. That means that for the first 4 years in Akatsuki, Itachi saw very little of Obito, considering he was partnered with Kisame. He had limited chances to even take out Obito. And even during the remaining three years, we saw Akatsuki just meet as holograms in order to seal the tailed beasts. That and if Itachi came after Obito with killing intent, wouldn't Zetsu alert him beforehand? Or wouldn't Obito just leave, like he did in the RTN movie, or like he did with Minato? Also, considering that Obito was the real leader, couldn't he just tell Nagato to tell everyone to attack Itachi at once? Itachi cannot handle all of Akatsuki coming at him.
-The point that MS Obito>MS Itachi and that Obito didn't kill Itachi because he was a pawn isn't very valid either. In fact it's a very desperate one imo. Obito knew the truth about Itachi and that he would never complete his main mission, which was capturing Naruto. Having Itachi in Akatsuki was pretty much useless for Obito, considering that he pretty much only helped with sealing the tailed beasts to our knowledge. If Obito could have killed Itachi, he would have. Then he would have replaced him with any other missing-nin, considering that there are quite alot in the Naruverse and they would actually want to capture Naruto. Obito didn't kill Itachi, because he could not. And saying that he didn't kill him due to "plot" is a lame excuse as well.
-Obito settled for making a deal with Itachi and told him to "keep his sharingan out of his plans". He didn't want Itachi to mess with the Moon's Eye Plan. What did he tell Itachi in order to keep him out of it and hold it as a deal? I'll kill your little brother and Konoha. He didn't say, "I'll just kill you Itachi". Why? Because he could not. He gained literally nothing from that deal with Itachi. It only succeeded in him putting a pause on his plans for 7 years. He could have found any other missing-nin to take Itachi's place, considering that Itachi did the bare minimum which was helping seal beasts. Another missing-nin actually would have done more than Itachi, like capture Naruto.
-Obito also did state that if he didn't keep his secrets (Izanagi) from Itachi, he'd be dead. That's alot better than that scan of Itachi telling a lie, considering that Obito was telling the truth there. That wasn't only caution, that was fear too.
-"Saying, what would Itachi do to Obito?, Obito faced Madara" is not very valid either. Especially when Obito had the rinnegan and Madara was caught of guard because he thought Obito was still on his side. That's the equivalent of saying, "What would Obito do to Itachi?, Itachi beat Kakashi in one second and Kakashi beat Obito in the kamui dimension." That type of logic is very poor.
According to the manga and how Kishimoto has portrayed both MS Obito and MS Itachi, Itachi is stronger than all forms of Obito bar the War Arc versions (any form that is higher than MS). It's just a fact that Obito fanboys cannot handle.