I just think Eichels' level right now as a complete offensive player is ahead of Matthews.
Truthfully - even though he is younger, I would say, career is Matthews thus far but peak performance right now goes to Eichel. Matthews' ability to consistently score as a center is amazing. And he's been a better two-way player (in his career) although I don't think you measure either guy by that standard...they aren't Bergeron or Barkov and they aren't supposed to be. But Eichel has been brilliant without a ton of help and is simply a better all-around playmaker.
So Eichel for me now, by a small but clear margin. But sure, ask again in 4 months and the response could be different. As an American hockey fan, I just hope they both keep growing and can join the likes Lafontaine, Modano and Kane as USA hockey legends.