Switch – Recommended Cisco storm-control broadcast and multicast threshold value for user PC

Well the first difference would be that switchport block unicast blocks unknown unicast and storm-control multicast blocks multicast packets.

The difference between switchport block XXXcast and storm-control XXXcast is exactly what you want to exclude in your question. You can pick any percent value for storm-control. It will block traffic of the specified type which exceeds this percentage of bandwidth on the port. switchport block is a simple yes/no. It blocks everything when activated.

Update:

As ytti mentioned, on some low-end boxes when storm-control multicast is exceeded all traffic will get filtered. In that case storm-control multicast is dangerous and useless.

Also on high-bandwidth interfaces (1/10GE) please remember that even a small percentage of the bandwidth can kill a box that punts the packets to the CPU. If possible use CoPP to protect the control plane. Also always use pps instead of bps for CoPP if possible.

Try enabling "storm control multicast level pps 1k 100" and enable the action when the level you just configured is reached: "storm-control action {shutdown | trap}"