I never tried NI therefore I can't comment on it or say its better than SS. However I do believe there's a difference between regular Clapton's and aliens. I personally use triple fused/quad fused or staggered fused Clapton's and always at 3-4 ID between 4-8 wraps depending on the RTA/RDA I'm using that day. The only time I use 2.5 with 7 wraps is in my old Aromamizer, because the chamber is so small that it can't hold 3mm. With that said tho, its great flavor but the emphasis lays on great. Its not amazing, good, outstanding in comparison to my bigger builds in bigger atties. I also believe that the wicking matters when it comes to flavor, of course it goes hand in hand with the design of the deck, coil positioning and airflow as a overall great result.
So maybe you positioning the coils differently, completely get different coils/wire, try different wicking material etc. Flavor just like everything is subjective in life, maybe you just don't like/enjoy stainless steel. Keep in mind, just because people say its far superior over other wires, doesn't mean you'll have the same opinion and/or experience. I love stainless steel but I wouldn't just use round wire or regular Clapton's, tried it and didn't get much satisfaction.
Find what you like and maybe its NI at the end who knows, but I defiantly would suggest trying 3mm ID with 6 wraps and see if that's better for you, if you want to keep the Clapton's.