I would say he is an upgrade 5 on 5 over Vatanen, it would only be a 1 or 2 year contract. I'm not sure anyone has the space to add him long term anyway. Last, it allows NJ to move Vatanen for a forward, preferably the LW version of Vatanen on an expiring contract.
You can't hold grudges for choosing one team over the other, NYC is a beautiful option for a professional and his family. This is all just a business.