Thanks for the script. The issue you are describing is different from the original post in this thread (although it might be related), where the user reported delays when saving hash tables as ini files.
I was able to reproduce your issue. It is taking longer because mIRC has to convert each line to/from Unicode/UTF-8 when loading/saving. Older versions of mIRC saved files as single-byte character data and did not require conversion. Unicode uses two bytes to store text, so it needs to be converted to UTF-8 before it is saved to a file. The UTF-8 then needs to be converted back to Unicode when it is loaded.
mIRC v7.02 is taking even longer because of the BOM handling. I have optimized that and it will be back to the same speed as v7.01 in the next version.
Regarding the CRLF difference: mIRC now uses a standard set of file-handling routines that are used consistently throughout mIRC. Older versions of mIRC were not consistent across routines in whether text ended with an LF or CRLF. The /hsave entry in the help file is referring to the difference between saving as text or as binary data, which is not related to this change.