Not the same kind of Dmen, overall, in terms of value I'd rank them as follows :
Makar -> Offense first Dman with good D skills
Heiskanen -> Two way Dman great overall
Dahlin -> Two way Dman very good overall
Hughes -> Offense first Dman with poor D skills
As a VAN fan, Hughes was a defensive liability this season, let us hope he can improve his Defensive IQ, maybe bulk up a bit. But he has a great shot and great offensive possession play. However I would trade him without question for any of the other 3 Dmen mentioned. On the other hand I get the argument that such great offesnive Dmen are harder to find than solid two way D.
The other thing, is that their performance cannot be isolated from the team they play in. Would Makar have as much success playing for another team ? I am not sure but his possession game is soo great from the highlights I have seen and he fits like a glove in COL. Would Dahlin seem more impressive in a team which is not BUF ? Most likely. Also as much as I like Heiskanen, he is playing within a good Dcore in DAL, which may make him look more solid defensively than he really is. I am very high on Heiskanen, in 2017 I thought he could be selected in the Top 2, given his Liiga season at 17.