Don't Mess With Old Plumbing Valves
Plumbing valves get old. When they get old, they tend not to want to operate like they once did. If I see an old crusty valve, rather than turn it off, I will shut off the entire house to avoid that old valve.
If plumbing valves are used regularly I doubt they would fail as often as they do. Gate valves are notorious for this. They sit in water their entire lives and 10 years later when you need to shut off the water to whatever plumbing fixture you are working on, the valve's gate shears off from the shaft. If this valve breaks, the gate may stay up and allow water to pass. At this point you will have to shut off the water to the house to service the plumbing fixture, which will probably cause the gate to fall into place and stop the water.
Your choices to get the water flowing to the fixture again are limited. Once you turn the water back on the house, since the gate is in the down positon, the water will not flow to the fixture. You might be able to remove the top of the valve and manually remove the broken gate. This will allow the water to flow again, but the valve will be useless...you will only be able to control the water to the fixture by turning on or off the main shutoff.
Ball valves don't fail nearly as often as gate valves since the shut-off mechanism is directly controlled by the lever. If the lever is parallel to the pipe, the valve is open and will allow water to pass. If the lever is perpendicular to the pipe, then the water will remain off.
If you are considering shutting off an old plumbing valve, you might consider turning off the main water supply to the house if the job will be reasonably fast.