Both fragrances start with a blast of incense. Interlude has an initial presence of some citric notes that burns off within minutes. Sahara Noir does not. After a few minutes both smell very similar; incense heavy. For the first hour or so I really could not tell any difference whatsoever! So close to identical to my nose that the scents are interchangable in my mind.
During the late middle phase both bring on a nice amber. Sahara Noir transitioned after a couple of hours whereas Interlude kept the heavy incense note longer before transition. For lack of a better word the amber in Interlude seemed to be a bit sweeter or a "higher" note than Sahara Noir.
After about 5 hours Sahara Noir seemed to be very close to a skin scent for me. The Interlude had more longevity by several hours. During the very final stages Sahara Noir's amber phase seemed just a little bit sour compared to the Interlude, even with just the tiniest hint of vanilla. Sour not in a bad way at all. Very delicious but compared to Interlude just a hint of sour.
I really find these two scents to be largely interchangable. Honestly, I love them both and find both to be full bottle worthy. Interlude lasts longer and seems to have just a bit more complexity by just a hair and longevity is better. Both are wonderful incense centric fragrances.
Since I have Interlude man I see no reason to buy Sahara Noir. Both are pricey. Sahara Noir is only availabe as a 50ml bottle. Double the price to get 100ml and you can have the Amouage in 100ml. Make your choice. A big bottle of Interlude or a small bottle of Sahara Noir. They both inhabit the same fragrance space.