Ian starts the story and has to build up to being dominant. Even now at chapter 10 the most dom thing he can do with Lena is choking her, after she asks him to. Axel on the other hand in one scene with Lena takes complete control of Lena, even making her lose a will point with the forceful blowjob. Remember Axel already was in a dom-sub relationship with Lena, before the game even starts. Axel already has a major head start in the dom department compared to people like Mike and especially Ian. He has an insane physique and his charisma is unrivalled, just look at all the moves he pulls on Cindy. I'd argue the only reason Ian can sleep with her first is because he has benefit of already being acquainted with her.
However just because he is physically dominant, sexually dominant, and extremely charismatic, doesn't mean he isn't one of the most insecure/fragile characters in the game. He spends the first half of the game grovelling for Lena's attention, at multiple points starting fights over his insecurity regarding his ex, and when he hears Ian might be with Lena he immediately gets aggressive. Also during the Cindy photoshoot at his house he makes snarky remarks about Ian's presence and when Ian tells him not to touch Cindy's leg he resorts to sarcastic comments, rather than being upfront. In other words Axel is great and dominant when dealing with women he can seduce, but the second he is put in a situation where he can't seduce his way out of, he relies on physical threats or schoolgirl level sarcasm.
Ian on the other hand has many paths so it's hard to evaluate him holistically, but let's for arguements sake we're talking about dominant/chad Ian. He can also seduce a lot of the characters at bars/clubs. Specifically Cherry, Emma, Alison. Women aren't instantly attracted to him like they are with Axel, he just doesn't have that height and that physique, but he can still seduce and act dominant in bed. Again he isn't a prior dom so he is still only just starting out in the game, he will get more dominant in bed as time goes on. Let him cook.