KISS tags
If you're already intimately familiar with the KO, I'd say no, it's probably not worth changing because they both perform similarly. Choosing between the two a year ago, I just thought the KISS was more clearly laid out and more fully formatted. It dictates the betting spreads and ramps for each number of decks. The IRC is always a positive number. You always start ramping up your bet at the same running count of 20 (with one deck or eight). It's pivot (the point at which it is perfectly accurate) is at a more common true count of +2 rather than at a rarer +4. It has 21 separate indices for basic strategy departure and 8 surrender indices.
Card tags are:
red 2 = 0
blk 2 = 1
3 = 1
4 = 1
5 = 1
6 = 1
7 = 1
8 = 0
9 = 0
10 = -1
A = -1
I like that it tells the experienced user how to fudge the larger indices depending upon current deck penetration, and how to play the marginal hands in true count mode. It also offers the option of counting all the deuces as plus one half, improving the efficiency some more. Right out of the book, you can take it further than KO. Those were my reasons a year ago and I'm down to the last improvement step now.