I stumbled on this post by TapamN and this help the solution:
There are the timing for loading a 256x256 .dtex texture (131kb)One issue you might run into is slow file access over ethernet. Using the C library stdio.h functions (fread, fwrite) can be much slower than using the KOS filesystem calls directly (fs_read, fs_write) when reading/writing large blocks. With stdio, you get something like tens of KB/sec, while with KOS you can get over 1 MB/sec. Stdio might be faster when preforming many very small operations. dcload-serial doesn't have this issue.
FREAD
BBA: 3300ms
Serial: 6100ms
FS_OPEN
BBA: 70ms
Serial: 600ms
I'll test with GDEmu and CD and update my result later.