Having an extra belt is always a good idea when you’re out in the backcountry or on the trail.
Mitsuboshi belts have a smooth back side and no more blue coating to flake off. Other benefits are a rubber compound vs urethane which has a higher temperature rating and is more flexible. One precaution is that the Mitsuboshi requires more care on setting the correct tensioning compared to the Gates belt that will operate both looser and tighter.
Belt and prices are added or subtracted from that price dependant on the size selected.