I just started playing Season 1 this month, it has been a pleasant surprise and has given me a lot of the SP needs that I was missing from SFV.
Personally, the way I see it, KI trumps SFV in single player aspects, period. Period. I think only a die-hard SFV
fanboy would disagree with this.
In regards to actual, gameplay mechanics, I like SFV better and feel it's more refined and 'smoother' for lack of a better term. I also feel that getting a MP win is more thrilling for me in SFV than in KI as from my relatively limited experience with KI (about 10 hours) it over-emphasizes and over-simplifies the combos. (Though take with a grain of salt as again I have about 10 hours in KI and probably a 100 hours in SFV).
IF SFV is able to beef up it's SP to the level of KI is now, IMO it will be a much better game than KI.
Both are great though.