FTP should never be used, because the passwords are transmitted in plain text and can be intercepted anywhere along the line. You should run FTP over your SSH connection, which automatically encrypts the communication with 256-512bit encryption. Almost all current FTP software supports SFTP and you use it the same way as normal FTP.

As far as Macs being more secure... this is based on the fact that less vulnerabilities have been discovered. Note, this doesn't mean that less vulnerabilities exist, just less time is spent looking for them since the Mac OS has such a small market share. The more popular the OS becomes, the more it will be targeted and the more vulnerabilities will come to light.

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