I can't speak to the cask strength Macallan because it's not available in my area but I recently drove to Georgia in order to purchase some Nadurra.
I think there is a great deal of confusion on Nadurra because it is a pure Scotch, none of the sherry, Bourbon overtones so common in many single malts. I especially deplore the taste of bourbon in Scotch, for me, it is an insult to the taste of Scotch and a complete turn-off and denotes a woeful period in the casking of Scotch whiskey. Sherry casks a far more historically acceptable and for enahnces rather than clashes in the manner of bourbon sour mash.
For me Nadurra and it's use of first-filled oak for aging sets a great standard for the true taste of Scotch. With it's high proofage I especially like to have it as a second drink after another Scotch. True it has a bit of a burn but I like that because it has a huge, long lasting finish. I can't bring myself to dilute this wonderful Scotch.
It doesn't have the peat overtone of many single malts but features a more wine-like, cognac-like nose and finish and despite some reviewers calling it one-dimensional I think it has one of the most complex flavors of any Scotch and has now become my standard for comparison.
I presently have a 56.2, 57.2 and 59.2 in stock. I love preceding Nadurra with a wonderfully peaty Laphroaig. Perhaps some might call Nadurra a dessert Scotch, and I might agree with that because I love dessert as dinner sometimes!