Really good poll. I think Panarin might still be slightly better right now, but I'd probably take Aho in the future. They actually debuted in the NHL one year apart, even though their age difference is 6 years. Since season one Panarin has been really good, hovering around PPG pace (looking to go over this season). Since he was already an internationally established player when he came in and because he is 27 already, I think he is somewhat "what you see is what you get" right now - with little room to improve.
Aho however has been improving tremendously every season, and seems to have the ingangibles to boot. Panarin is like an elite mercenary winger that's a great add to any team, but Aho is tracking to be a #1C with captain responsibilities and who you can use in every situation, scoring at PPG. Right now he has 10+ more points than his next best teammate at - again - the age of 21.