Frankly, I never had the choice between nickel and stainless steel strings. Any strings containing nickel immediately results in intense blistering all over my fingertips, making playing the guitar mostly impossible.
According to Daddario, these are completely nickel free. I have noticed immediately that it takes a lot of playing before blisters occur, mostly due to the fact I need to change my frets to something nickel-free also. It's unfortunate, but these strings are super awesome!
They are very bright compared to my previous 9 guage nickel wound strings, but I don't necessarily hate the sound. Personally I prefer a warmer sound, but these are the best I can do. If you like something bright and quite twangy, these are definitely for you.
The colour coding is phenomenal! Super handy and personally I think it looks quite fun. These strings offer phenomenal sustain when played through an amp.
I really would recommend these for a bright tone which cuts through a mix quite nicely! Amazing for those fellow guitarists whom struggle with the terrible nightmare of a nickel allergy.