It depends on what you want to achieve. Long story short:
-> If you mirror SRAM to EEPROM, mirrored part can be a part of NDEF msg (NDEF is always in the beginning of user memory) so you can read out SRAM value with NFC Mobile, without app needed.
-> But if you use SRAM in normal location (no mirroring), then you use it for pass-through mode more likely, then you need an App - because you need to tell SW (App) where to write.
In conclusion, if you plan to be writing raw data to the SRAM directly from the Smartphone, use pass-through mode.