I feel like what you probably mean is that Yu is more forgiving of mistakes? What I mean is, if Yu isn't spacing himself perfectly, he sort of doesn't care... his normal hitboxes cover like half the screen anyway. Whereas Chie just sort of dies if she ever whiffs a move, and if she isn't spaced perfectly, she's almost certain to whiff something. Aside from that fact, Chie does generally have the mobility advantage (as long as the Chie player can block the slide kick and dive kick).
My understanding so far is that Yu's moves are generally a lot more unsafe on block, though. So a Chie player who can successfully defend against Yu until they get the opportunity for that one good hit is going to be able to convert into a higher damage combo than Yu is capable of? I'm also kind of convinced Chie's oki really is stronger. Which is not to say that Yu's is bad, but a blocked 5DD from Chie sort of locks the opponent in place for a second, and gives her a second mixup opportunity, whereas Yu is really just going for a good single hit on wakeup, and if you block/recover right, then you got out. Which all means that as player skill increases, I think Chie gets steadily stronger in this matchup.
All that said, the more I play the specific Yu v. Chie matchup, I do think Yu really is advantaged. He can punish a lot of stuff Chie does with his instant start-up supers, including easily hitting her out of meteors on reaction, whereas Chie has trouble catching him with a God hand because the range is so specific. Also the fact that Chie's All-out attack is so fast actually causes it to lose to Yu's all-out attack because those moves have armor, which is incredibly annoying and kills me all the time.
All that said, I could have no idea what I'm talking about...