I have worked in a development team that had both priority and severity. The main difficulty I encountered was that people would silently factor one into the ot

I have worked in a development team that had both priority and severity. The main difficulty I encountered was that people would silently factor one into the other. Some would factor severity into priority (This is a crashing-type bug, so we should prioritize it), or priority into severity (This bug only causes minor harm, so it's not a high priority for us). But this was done silently and unconsciously, and different people had different directions for how they would do it. Due to this experience, I think one metric is best.