Obito Uchiha would likely win in a fight against Itachi Uchiha based on a detailed comparison of their abilities and combat styles.

Reasons Obito Would Win

• Superior Skills and Techniques : Obito possesses a wide range of powerful techniques, including the Kamui ability, which grants him intangibility, allowing him to phase through attacks and defenses that Itachi cannot counter effectively

• Durability and Chakra Reserves : Obito is more durable and has larger chakra reserves than Itachi, who is known to be chakra-poor and physically sick, limiting his stamina in prolonged fights

• Countering Itachi’s Attacks : Itachi’s main offensive tool, his Susanoo (including the Totsuka Blade), might be ineffective against Obito’s intangibility. Obito can walk through Susanoo and other physical and chakra-based attacks, significantly reducing Itachi’s options to deal damage

• Izanagi vs. Izanami : While Itachi’s Izanami can counter Obito’s Izanagi, the latter is a powerful technique that can erase Obito’s death and allow him to survive lethal attacks. Obito’s use of Izanagi has been demonstrated to be a key factor in his survival and victory in fights

• Strategic and Tactical Edge : Obito’s intelligence, strategic thinking, and ability to use multiple powerful jutsu simultaneously give him an advantage over Itachi, who lacks the speed and stamina to maintain continuous pressure

Itachi’s Chances

• Itachi’s best chance lies in quickly summoning his Susanoo and using the Totsuka Blade to seal Obito. However, the effectiveness of this sealing technique against Obito’s Kamui intangibility is uncertain

• Itachi’s arsenal, including Amaterasu and genjutsu prowess, could create openings, but Obito’s ability to phase through attacks and maintain distance reduces Itachi’s effectiveness

Conclusion

Despite Itachi’s formidable skills and fan-favorite status, Obito’s superior durability, intangibility, chakra reserves, and versatile techniques give him the upper hand in a direct confrontation. Obito’s ability to counter or bypass Itachi’s main attacks makes him the likely winner in this matchup