not talking about potential or whose the better player in the long run. I want to see who everyone thinks will make a bigger impact in their first few seasons in the league. In other words, who'll make the adjustment to the NHL easier?

Simple answer: Whomever the Devils take 1st overall. Probably Hughes. They have the better roster right now, in my opinion. They're closer to contending. Plus, Hughes could put up huge numbers next season if he centers Hall and Palmieri or Hall and Bratt. However, I might change my mind if the Rangers land a big time UFA like Panarin or Duchene this summer. Both teams have the cap space to be big spenders this summer and the UFA pool is loaded w/ high end talent.

Kakko has already been playing against men in Liiga and has NHL-ready size, so I think he'll become acclimated quicker. Hughes is smaller and has been playing mostly against his own peers, although I do think he has the higher ceiling.

Kakko just dominated a men's league as a 17/18 year old, and is the more polished player right now. I'd honestly expect him to get around 60 points next season, even if the Rangers don't add a key piece. But if they do end up with Panarin, imagine a Panarin-Zibanejad-Kakko line. That'd be nuts.