What's the difference between mnt vs media?

I recommend visiting the Filesystem Hierarchy Standard.

• /media is mount point for removable media. In other words, where system mounts removable media. This directory contains sub-directories used for mounting removable media such as CD-ROMs, floppy disks, etc.

• /mnt is for temporary mounting. In other words, where user can mount things. This directory is generally used for mounting filessytems temporarily when needed.

Ref:
http://www.pathname.com/fhs/pub/fhs-2.3.html#MEDIAMOUNTPOINT
http://www.pathname.com/fhs/pub/fhs-2.3.html#MNTMOUNTPOINTFORATEMPORARILYMOUNT

use /mnt for stuff you mount by yourself

leave /media for the system to mount its stuff