It's not one or the other - you use both. You only use r1 Rapid Slash with the two rubies which allow it to generate more CA. Those rubies are also right by three core stat rubies, which make them not a waste at all.
You want to use r3 Kick (or Punt), and r1 Rapid Slash in almost any endgame build.
I was saying that Rapid Slash is better for generating CA, which it is. But that doesn't mean Kick isn't useful as well. They're two different skills for two different purposes.
Anyhow, every player is free to build their character however they like, but before offering "fixes" to people's rotations, or alternative builds, I suggest you do some reading, and maybe reach endgame first.