I think intangibles are much better. Mitchell is a great leader. Work ethic is better. Mitchell has gotten better every year, Simmons has not. Ball handling is probably better too. Mitchell also has been really good in the postseason the past two years. Simmons has been average. Most advanced statistics favored Mitchell last year too.
The biggest thing for me though is fit. The one thing you say Mitchell is better at than Simmons is the most important thing in the NBA right now. Mitchell is a good enough creator (assist numbers aren’t high for anyone in Utah’s system) that he could play point for the Sixers and the spacing he’d provide would be exponential over Simmons. Just my opinion.
Really pointless to discuss though because Utah would never do the trade and maybe Philly wouldn’t either. Simmons and Gobert are unplayable together.