Seems like Austin would have to be the favorite here. His range, power and handspeed would no doubt be a handful for Tapia. Tapia's own handspeed and combination punching would give Austin trouble but you'd have to figure over the long haul Austin's powerful lefthand and right hook would have Tapia somewhat tamed.
Austin never impressed me much. A big, entertaining puncher, for sure. But nothing special IMO. He may have been a tall, long-armed fighter, but he wasn't taller than Nana, or Tapia himself. I think Tapia out-boxes him clearly, if he fights smart. Just a more well-rounded, better fighter.
Why on Earth would Austin be a favorite over a HOFmer with a miles deeper resume than him? I think Austin has his moments, but ultimately Tapia is too good a technician for him. Tapia 8-4
Just saying, you're pointing to tapia's credential as a HOFer like it's evidence he beats Austin. Austin's biggest weakness was durability. Tapia can't exploit that at all. And there's a lot of lesser fighters than Tapia at bantamweight that could beat Tapia, starting with Ayala.