I think it's pretty close right now and leaning toward Barkov. He has similar and arguably more talent in a bigger frame, and had both the high scoring season Pettersson hasn't had as well as a dominant defensive year. He also was playing through injury a lot of this season so it's possible his numbers are a bit deflated. But he's also a bit of a weird player who hasn't really translated his skills to production save for that one season, and who can be very good defensively, but hasn't succeeded in doing so in recent years. In general, his production outside of '19 has hovered around what Pettersson has put up since he's been in the league, and that's with him playing more minutes.
Meanwhile, Pettersson's underlying numbers this year were very good, even though I think they look a little better due to good teammates and poor depth behind him. Pettersson was better this year, but you could argue Barkov was off due to injury and has the track record. With Pettersson's age, it's possible this is just the start and he will keep being better than Barkov, which would make him better now. I still feel like Barkov would be a little safer
Meanwhile, Pettersson's underlying numbers this year were very good, even though I think they look a little better due to good teammates and poor depth behind him. Pettersson was better this year, but you could argue Barkov was off due to injury and has the track record. With Pettersson's age, it's possible this is just the start and he will keep being better than Barkov, which would make him better now. I still feel like Barkov would be a little safer