SuperSU Pro adds the following features to your SuperSU installation:
- OTA survival mode (no guarantees)
- Full color-coded command content logging (input/output/error)
- Per-app logging configuration
- Per-app user override
- PIN protection
See the SuperSU app description for further details on SuperSU.
Note that SuperSU Pro is rarely updated - most of the updated code goes directly into the main SuperSU app. That is the one you need to update.