More info is needed, I assume it is not the league in sig, are you in rebuild mode or contending?
I have been the only owner of Klingberg in my Roto League. I live in Arkansas and we get a lot of Stars games. I saw him play his first two or three games and when I was watching him play a game in which he got his first three point game I quickly ran and added him that night. I reached a bit early for him in last years draft too. I am open to trade him in my keeper for the right return but it will take something decent in return.
Klingberg is in place to be the ONLY option on PP for a high scoring (top 5) team. He has two seasons of very similar numbers to compare and seems to be able to continue production at this same rate or more next few years. He gets to play the power play with Sharp (60P) Spezza (60P) Seguin (90P) and Benn (90P).
Hanifin is still behind J. Faulk for power play time and could even be behind J. Wisniewski (who we do not know what Carolina will do with yet) His best offensive weapons are very unproven or unimpressive at best. This team is not a lock to improve in any way next season. 50 point value could be 2-5 years away
Ekblad is two seasons into his NHL career and both season are pretty much a mirror image of each other. No doubt he will increase as he develops, however, he is two seasons @ 0.5 points per game. His shot rate has increased, which I really like for defenders! He is on a young team which WILL improve next few seasons but maybe not without regression along the way. This year the panthers were very good and there is a chance not every one produces like this again next year. 50 point value could be 2-3 years away. I would like to point out the Dobber Ramblings that discuss Ekblad in the last few days. The point was made that Brian Campbell is a FA and how that could change Ekblads performance. In a nutshell he is not very good without the very experienced Campbell playing with him. This could be important or not to you in your choice.
I would not take this trade unless I was in rebuild mode and had a very prospect heavy roster. If that is your situation you are getting a very good return, maybe even the top two young defenders in the NHL.