It doesn't matter which one you download - both include installation setup for SEPM - and thats what is needed to fix the vulnerability. On the difference between both:
- Symantec_Endpoint_Protection_12.1.4a_SEPM_EN.exe - only SEPM installation
- Symantec_Endpoint_Protection_12.1.4a_Part1_Installation_EN.exe - includes SEPM installation and additionaly installation packages for SEP clients in version 12.1 RU4