When should the xlsm or xlsb formats be used?

Question

Since Excel 2007, Microsoft has split the classical .xls format to several formats (in particular, .xlsx, .xlsm, .xlsb).

Answer 1

The XLSB format is also dedicated to the macros embeded in an hidden workbook file located in excel startup folder (XLSTART).

A quick & dirty test with a xlsm or xlsb in XLSTART folder:

Measure-Command { $x = New-Object -com Excel.Application ;$x.Visible = $True ; $x.Quit() }

0,89s with a xlsb (binary) versus 1,3s with the same content in xlsm format (xml in a zip file) ... :)