The problem I have with Harden is that he monopolizes the ball. Not to the extent that Russ does it, but still quite a lot, which means that his teammates will be called shit from people and pundits (Oladipo didn't play that well when he was with Russ, while now he is a superstar). It would be very difficult for him to win a championship, I just don't see it happening.
On the other side, Steph makes everyone better and it is never about him, it is all about the team. Not many (if any) superstars are as willing to share the ball at him. Heck, he was the back-to-back MVP, having already won a title, and he didn't mind sharing the ball with KD, allowing him to even be No.1 in the first playoff. He still wants to play with KD despite that means that he probably won't ever get a finals MVP. It is all about the team, not him.
LeBron is in a league of its own, Steph and KD are after him. And then there is the bunch of Leonard, Harden, Giannis and AD (IMO in that order) for me.