Kyrie is the best pure scorer compared to those two but overall obviously they are both easily better.
Thing is though, Kyrie is absolutely perfect where he is, Cavs don't need another all round powerhouse with LeBron in there, what they need is someone to take the scoring burden off LeBron and allow him to basically play in the Magic Johnson mould with someone who can blitz the scoreboard when it's needed and that's what Kyrie is great at. He's a better fit with LeBron than Butler or PG in my opinion, while obviously either of those two would also be fantastic there.
That's true. Kyrie as the main man would IMO fail to elevate his team to a higher level but he's great as a 2nd man on a contender. He's actually a point guard who is fine stepping aside when LeBron needs to handle the ball and fill playmaker role, not many in the NBA who would do this well under circumstances. Imagine Westbrook playing next to LeBron