#1 WWE having Bianca Belair face Asuka gives the company more time to tell a story
Although WWE would have an variety of opponents for Bianca Belair to face on SmackDown, moving the EST to RAW would give her more time to grow her character. The company would also have even more television time to build on Belair's eventual WrestleMania title match. (RAW is always an hour longer than SmackDown.)
It's no secret that WWE is relying on established talent to help fuel ratings, so Belair is still in a very vulnerable position. Many fans still remember the disappointing women's matches at WrestleMania 36, so Belair is facing an uphill battle. She's not a firmly established star yet, so The Showcase of the Immortals could be a make-or-break moment for the popular competitor.
With that being said, facing Asuka would give Belair a chance to flesh out a compelling story for her first singles WrestleMania title match. By facing a legitimately tough champion, WWE would present Belair with a more daunting challenge, which could help the EST reach the next level of stardom.
Facing Banks could help Bianca Belair achieve the same goal, but Asuka might be the safe bet in WWE's mission to help the challenger reach the next level.