If it were me, I would suggest doing both. Your Mini at the most has a 64GB drive. Just setup a partition onto which you can use SuperDuper or CCC for your image backups. Use the other partition on the drive for TM backups. They both have their advantages (TM for long term backups, and Dump based for booting off of it in a pinch).
As for backing up to a TM location on the network, the only way to do this is to trick TM into letting you. You just have to run this in a terminal:
# defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1
Just make sure you have TM disabled in the prefs, and then have your SMB share mounted up before hand. Once done, re-enable TM and it should see the SMB share as a valid destination.
One thing to note on network based backups, is that it creates sparsebundle files like a Time Capsule backup, rather than flat files like a USB based backup. These can be finicky, and can go corrupt if you cancel your backups in the middle, or move your laptop from the network while its trying to backup. If you have too many failed attempts, you may find it will refuse to backup, and requires you trash your old backups to get things going again. Be warned!