A common mistake when analyzing network speed/bandwidth between different applications and servers is to fully rely on the mere size of the files being transferred. In fact, one big file will transfer much faster than thousands of small files that have the same accumulated size. This depends on the overhead of reading/writing these files, building TCP/IP sessions, scanning them for viruses, etc. Furthermore, it is application dependent.
I built a small lab with an FTP server, switch, firewall, and an FTP client in which I played a bit with different file sizes. In this blog post I am showing the measured transfer times and some Wireshark graphs.