Stealth
This is not because of MariaDB but because aapanel itself is not optimized with MariaDB. This has been voiced by the aapanel side. They are just optimized and recommended to use with mysql instead of mariadb. As for performance and differences between mariadb and mysql, you can see a lot on the internet and I myself have found mariadb to be more stable. I have about 30 vps using a large database with each data having about 300k - 400k rows of data for each table, so in the process of using both, I found mariadb to be more stable and optimal in performance.