A 9 year age gap means there’s a lot at play with the question. McDonagh was undoubtedly the better defenseman this year and I’d take him to win now. It’s also possible the bottom falls out, he’s more expensive next year and has another year after that.
For the Canucks, McDonagh would improve the defense for now, but would also take up a lot of space when Hronek needs a new deal, Zadorov is a UFA and they need to improve the right side. They also have Hughes and Soucy locked in on the left. Chychrun would be cheaper for next year but he was also bad defensively this year and is a UFA to be who needs to get paid.
To be honest I think I would move them both rather than keep them, and if that’s the case I’d take Chychrun since I think he has more value. He was moved last year for a 1st and two 2nds. McDonagh was just moved for a 2nd, 4th and 7th. While Chychrun’s value has probably gone down after the year he had and with only 1 year left on his deal now, I think he’d still bring back more than McDonagh did.