Some distinctions are obviously easier than others. I would have to fund both the bridge repair and the water supply because they both have immediate health and safety issues attached.
We have to rely on our elected representatives having the wisdom and appropriate priorities to make those difficult decisions. They've not always done a very good job (you may find that to be the understatement of the year). But on the other hand, we are still one of the greatest countries in history, and that is not despite our government but more because of our government.
When a coach has tryouts for the basketball team and 40 kids try out for a 12 man roster, cuts are never easy. You will have 6 that are easy picks, 10 that are easy cuts, 4 that are fairly easy picks, and 10 that are fairly easy cuts. The coach is now left with 10 kids fighting for the last 2 positions. Here the coach just has to make his best decision based on a number of criteria and know that he may be wrong (only having limited time to evaluate). There will be kids and parents that disagree and complain but that's unavoidable. The line between the 12th and 13th player is so small and open to interpretation that there will never be universal agreement. The coach is hired and paid to make that decision and live with the fall out.
Politics and the budget process are the same. I always agree more with the picks of the democratic coaches. The problem in politics is that they don't want to cut the roster at 12, they want to keep 25. And then there's just not enough playing time to go around and dissension quickly sets in.