Hello @Awing,
Not only the Flash size but the SRAM too:

There are a few different specifications,
Table A-5. Thermal Package Characteristics (9S12XS256)
Table A-6. Thermal Package Characteristics (9S12XS128)
Table A-12. Run and Wait Current Characteristics
These two parts have different masks:

S9S12XS256J0CAE 0M05M
S9S12XS128J1CAE 1M04M
The RM specifies different part ID numbers:

Each mask revision has a different errata document:
https://www.nxp.com/products/processors-and-microcontrollers/additional-mpu-mcus-architectures/16-bi...

Regards,
Daniel