Well after testing with Bryce on multiple different file size and different array sizes and looping only one method at a time and both at the same time, etc...

The FSO method is only about .07 seconds faster on average for a file size around 800K but is just about 1 second faster for a file size of 8MB then using the Variable Incremental method in ReadFile() by Christophe Melin above. The Constant method is quite slow in comparison.

In general for a single run script on a small file probably no real difference. However if you need to run something on a large file or many files all day long then the FSO method will be faster by the end of the day.