According to hwtests, older versions of IOS are slower at performing
various filesystem operations:
https://docs.google.com/spreadsheets/d/1OKo9IUuKCrniz4m0kYIaMP_qFtOCmAzHZ_zAmobvBcc/edit
(courtesy of JMC)
A quick glance at IOS9 reveals that older versions of IOS have a
simplistic implementation of memcpy that does not optimize large copies
by copying 16 bytes or 32 bytes per chunk, which makes cached reads
and writes noticeably slower -- the difference was significant enough
that the OoT speedrunning community noticed that IOS9 (the IOS that
is used for the OoT VC title) was slower.