TL:DR nvarchar(max) is inefficient and should be avoided.

Queries against an nvarchar(max) field use more kb than queries against an nvarchar(10) field, even if the data stored within the two fields is the same. So the performance will be noticably and measurably worse, which should be avoided.

At 47 minutes Tim Corey provides a pretty good explanation of this, complete with outside sources: https://www.youtube.com/watch?v=qkJ9keBmQWo.