Dear @NFR
There is no functional difference at all, this is the same Silicon and package and features. Except the One ending by "J" has a software enablement feature that you can run our embedded Java inside , which is deescribed Here : https://www.microej.com/news/stm32java-development-environment-for-stm32-microcontrollers/
So if you do not need to run Java ecosystem it is transparent for your application.
Ciao,
STOne-32.