Stone.
Over the past 3 seasons:
5v5, Stone has 106 points over 186 games for 0.57 PPG 5v5.
All Sit, Stone has 171 points over 186 games for 0.92 PPG.
5v5, Panarin has 140 points over 218 games for 0.64 PPG 5v5
All Sit Panarin has 223 points over 218 games for 1.02 PPG 5v5
So you're basically losing 0.07 PPG 5v5 and 0.10 PPG overall for a guy that is far better defensively, has had tougher deployment on a worse team, and could very likely cost you less AAV.
You are losing all of 6 points 5v5 per season and 8 points total per season for a much more versatile and potentially cheaper player.
Easy choice.