I would put them very close right now.
I would give Stutzle a pretty significant edge on the PP, pretty even offensively at ES, and I can only assume Lundell is a better defensive player than Stutzle currently (although that's a bit of a guess... can't say I've seen enough of Lundell to get a great idea of his defensive zone play).
Lundell definitely had better line mates - lots and lots of Reinhart & Marchment, and when he wasn't with Marchment he was with Reinhart + Verhaege or with Vatrano (to a lesser extent)... then a smattering of Mamin, Huberdeau, and Duclair.
Stutzle, on the other hand, was mostly played with Formenton and a combination of Brown and... Gaudette! Next on the list is Paul, then Batherson, then Tkachuk, then Norris... point is, while he played with some good players, his main linemates at ES were far below those of Lundell.
I think Stutzle will separate himself in the future, however:
1) Both players need to grow into their frames more, but Stutzle is a far more physical player and I think an increase in strength will have a greater impact on his play than the same growth will have on Lundell.
2) Lundell may always be better defensively, but Stutzle has the smarts, the effort, and the commitment to improve that makes me quite confident he will be a good defensive player.
3) Stutzle's skill and offensive IQ are simply on a higher level. He also shoots & skates better. Lundell may be the better passer.
4) While Lundell will likely be a very good PP player, Stutzle already is a dynamic threat on the PP and will continue to improve.
5) Stutzle will draw as many penalties as anyone over the next decade. As he grows stronger, he will shed the diver label and will just be a raging bull who opponents cheat to stop.
Right now, I would say they are both good 2nd liners. Lundell should be an elite 2nd C or a solid #1C, but I think Stutzle can and will be a borderline-superstar C. I didn't think this way before last season... thought he would be an allstar, 1st line winger. But he quieted a lot of my concerns over the course of the year.
Lundell easily. Kid was always going to be a stud from day one.
Saying "easily" discredits you pretty immediately. I can see why someone takes Lundell today and moving forward. If you think it's not close, well, then you must think Lundell will be stealing the #1C job from Barkov pretty soon.
Both are stud players, right now, and both will continue to grow.