Stone will be cheaper. Perhaps as much as $3 mil+. That surely matters. Do I want Stone MORE than them? No. He's amazing, and beggars can't be choosers, but Panarin (we'll bring him up first as another winger) is a much better fit to me, besides being a better talent.
This team needs a dynamic, shifty player to bring out the potential in all their other players. As good as Stone is -- which is to say better than anyone -- his skill-set as a somewhat sluggish 2-way PWF and PP net front isn't as important for this group, which is a bit overflowing on those (to whatever talent level). Panarin is a PP half wall QB, has elite puck skills, a better shot, is faster, and just better offensively as a whole. I'll also be the first to champion signing Stone in lieu of Panarin. Stone is the perfect winger to have once you already have a Panarin type is how I look at it.
As for EK, again, you're talking about a top 3 d-man in the league. Health concerns, cost, age are all relevant. But again it's about fit and pure talent, and him playing 25 minutes a night impacts this team more than Stone.