Ryu's gap-closing isn't as great as some give it credit for. His best safe gap-closer is 4P+K/ongyoin 6P, but it is a high (crushable) and like most of his options, can be side-stepped. His teleports are the same old business, and esp. someone with Pai's speed really doesn't have to worry about them. His best spacing techniques are really baits, such as 7P->Shoho but the efficiency of these is greatly reduced with characters who have good lurch or speed (Pai in the latter). Free-cancel mix-ups simply don't work with Ryu's speed as Pai can start her next attack after Ryu and still beat him out. Similarly, many of his strings can simply be interrupted. Certain frame advantage moves are similar. For example, with his 3H+K or 214P, even on block Pai will still be tied for speed with his fastest mid. While Hayabusa is not slower than Bayman, compared to Pai his speed is still a large obstacle because you'll always be at a disadvantage in neutral (crushing doesn't work because Pai's 11F mid will beat out pretty much everything). Hayabusa's range techniques can be easily circumvented by side-stepping or simply intercepting them with superior speed, and that's assuming you can make distance to begin with.
In the end, it really boils down to what I was talking about earlier with Bayman. In 90% of situations against Pai, there is no favored course of action because her options will consistently beat out Ryu's. He must guess right. Exactly right. Granted with the Izunas he does get good damage off of a proper guess, but I feel like if you're relying that much on "blind" (I understand there's more to it than that, but it can feel that way given how many of Ryu's options can be beat-out by Pai's) guessing, it's really not a 50/50 scenario.
6KP can honestly be intercepted or held
3H+K... yeah...
4PK is really the big useful one, and is really more of a "hold in anticipation not reaction"-type thing. But obviously he's losing that in 5U
In the end, it really boils down to what I was talking about earlier with Bayman. In 90% of situations against Pai, there is no favored course of action because her options will consistently beat out Ryu's. He must guess right. Exactly right. Granted with the Izunas he does get good damage off of a proper guess, but I feel like if you're relying that much on "blind" (I understand there's more to it than that, but it can feel that way given how many of Ryu's options can be beat-out by Pai's) guessing, it's really not a 50/50 scenario.
1KP is easy to hold, ditto 4P+K & ongyoin PPPI still am at wits end that good players can't hold his guard breaks on reaction though.
6KP can honestly be intercepted or held
3H+K... yeah...
4PK is really the big useful one, and is really more of a "hold in anticipation not reaction"-type thing. But obviously he's losing that in 5U