People are too paranoid about clear text protocols. If you're running FTP on your LAN (which is the only place something like SMB would be run can't imagine anyone using over the internet same goes for NFS), and you are worried about man in the middle you got way bigger problems than FTP if you already have an "attacker" on your inside network with the ability to intercept that traffic.
FTP is probably less vulnerable, in that there are generally far fewer "exploits" against FTP servers than SMB systems.
Biting the hand that feeds IT
