All MasterUpdate does is flag all your esps as esm, nothing else.
The reason this is done is because esps have certain problems that esms dont suffer from.
This is Not correct. Taken from the Fo3Edit manual:
Master Update Mode is activated by creating another copy of the program, and renaming it to, “FO3MasterUpdate.exe”. When FO3Edit runs, it will recognize its filename and run in Master Update Mode accordingly.
When Master Update Mode is activated, the following operations are performed without further user interaction:
? All modules in the Data folder are assigned into 2 groups, masters and Plug-ins, based on their file extension (.esm or .esp).
? The modules in each group are sorted by file modification date/time.
? All module files are re-dated, first all masters, then all Plug-ins, in 1 minute intervals.
? All active modules are then loaded, the ESM flag set in the file header if not yet present, and the ONAM sub records build if required.
? Any temporary overriding world space record that has at least one previous version that is persistent is marked as persistent.
? All modified modules are saved.
This process will result in a better-integrated group of mods, and will likely result in less crashes than without having run Master Update Mode.
The link to the manual is in my sig, it should answer most of your questions. let us know if you have any more.
Cheers,
Kris