I don't really think that is an assumption that can be made, his Chi changing move has to do something (it appears to have two different forms, maybe more), which is definitely likely to change up the way he plays. Definitely more complex than the likes of Captain America.
I was trying to compare him to Vergil; however, I was extremely unclear with that. I apologize.
Iron Fist's 3 chi power ups are revealed to be a power up, defense up, and a meter boosting buff. I'm really interested to see how much of a difference each power up makes. We kind of get a taste in the reveals for how much crazy damage the red buff does though.
On a side note, he's reminding me of She-Hulk. Seems to hit really hard and even has a deep cross-up jump C. They both also seem to be lacking in mobility (i.e. no airdash, double jump, teleport, projectile) as well.
I'm also really hoping that Vergil's crossup move isn't invincible.