I don't really disagree with any of this, but at the same point, you can come up with similar pros for keeping Hagelin over Hornqvist. I don't think Hagelin only being signed for 1 additional year is a negative, and he has the big advantage of being able to play with any center on this team and fitting well. I wouldn't say keeping Hagelin would be the "better" decision in terms of ES play, but it would be the decision to give them a lot more flexibility. I think Hornqvist is dramatically harder to replace than Hagelin and is just a flat out better player, but at the same time, he'd leave the Penguins limited with options to run with at ES, he'd cost more than Hagelin and it might be difficult to move Hagelin anyway (although I doubt it since he'd only have 1 year under contract left). That's why I was saying it's not a simple question, there are pros and cons for keeping each of them over the other.
I'd like to re-sign him, but I'd be a little concerned with how the ES lines would play out if CH doesn't play together, or if both Kessel and Sprong are on RW. If one of them moves to LW or gets traded, I think that solves most of the issues at ES. You can then have Sheary or Rust as your top line RW, Kessel or Sprong as your 2nd line RW and Hornqvist as your 3rd line RW. However, if your top-9 RWers next year are Sprong, Kessel and Hornqvist, you're kinda limited with options if Crosby is calling the shots for who is on his line.