At risk of oversimplifying, Ostlund and Helenius seem like mirrored offensive and defensive versions in the same tier of middle six C prospect.
Ostlund is a better skater, better vision, better skill package. Helenius is more powerful, better defensively, more heart and soul. And there's plenty of overlap in their games.
Ostlund is two years further along in his development without really faltering or breaking out yet. Helenius obviously hasn't had the opportunity to do either yet.
I imagine I have them closer than most here. Ostlund was #30-50 on most league-wide rankings last season. Very interested to see where each lands on new lists in a few months.
EDIT: I should say I have Helenius just ahead because he has the physical make-up to basically already have a floor as an NHLer. It's a big head start for a draftee, as long as he isn't close to the end of his runway. Ostlund still has to reach that milestone, but his ceiling remains huge. He was electric against top comp at WJC24.