If it were just about the player, I think I'd keep Nurse ahead of Klefbom. I do love the idea of the solid Swedish pairing of Klefbom-Larsson, and their greatness in the 2016-17 season cannot be denied. However, as others have said, Nurse has an amazing skillset and appears to be very close to equaling Klefbom in total effectivness, with room to grow more even.
But, there is contract status as well. Klefbom is signed on a VERY nice deal for many years. With Nurse, a lot is in the air right now. We shouldn't expect him to sign the exact same Klefbom deal, because of cap growth. If he would agree to 4.5 million (ish) AAV that would be great, and the more years, the better.
I'd say that the contract issue could make Nurse more tradeable.
However, I feel this should be the goal, long term:
Klefbom-Larsson
Nurse- [Right shot offensive Dman]
XXX-XXX
So, that puts it on Chiarelli to either trade away Sekera and Russell, or manage the cap to keep them as an expensive bottom pairing (that would be an amazing luxury to have, but a luxury)