Hi Swagatika,
You can read the developer documentation here: https://docs.mendix.com/releasenotes/studio-pro/9.0/
The blog with more marketing content is here: https://www.mendix.com/blog/mendix-9-0-where-it-all-comes-together/
From my experience, the upgrade is def. worth it.
So much great improvements to the developer experience are added in the way styling is handled, page parameters, etc.
Have fun,
Peter