My argument for Panarin is that he kinda checks the box for "free agent of the quality which does not come available every year or two or three." He's produced high, high numbers in two stops, and he's only got 4 seasons of NHL mileage on him, which is important when considering his age. He's a young, low mileage 27 years old, who has been remarkably consistent across his four years with the Blackhawks and Blue Jackets: 27-31 goals, 43-59 assists, 74-87 points. That's basically second tier of NHL star (behind the Ovechkins, Crosbys and McDavids of the world), and you are probably gonna get that production for longer than the average 27 year old.
Duchene strikes me more as the type of guy we get into trouble with. Big name and a high price, but has been bounced around for different reasons than Panarin (who was only traded to reunite old teammates in a quest to re-establish chemistry, not because the team had moved on from Panarin). His high point total is 70, not 87, and he has plenty of up and down throughout his career so far: seasons of 59, 41 (!!!), 59, 55, and 28 points (though in a less than full season, but one in which he still played 58 games). Etc. He also is WAY higher mileage... he's been in the league since 19, and has a full ten seasons of service. He's gonna age more rapidly than normal, most likely. I mean, christ, this guy just screams that he's gonna come to NY and put up 45-55 points and be an unmitigated disaster at 9 million a season.
I'd happily pay 11 million to Panarin and his 75 points if only to avoid getting sucked in on Duchene. Yes, I know we need center options, but Zibanejad is young enough to be one, we have assets to trade up and get another top 6 center this year, and if not this year, we'll have assets to trade up and get another top 6 center the year after in a center-strong draft. On top of that, Chytil, Andersson, and Howden are all probably middle-6 capable centers (if not better), especially if their wingers are Kakko, Kravtsov, and Panarin. You can get by with a second line center only putting up 40-50 points when you've got 70-80 point wingers flanking him on both sides.