Answer: First, valve selection should be based on technical application (sizing, flow capacity) and company standard requirements.
Ball valves and plug valves are generally quarter-turn valves (90o to open and close). Ball valves are generally less expensive, require no lubrication, can be pigged, and provide tight sealing with low torque.
Although ball valves are sometimes used for throttling (adjusting the restriction to control flow), they are most effective when fully open or closed because the seals are subject to damage due to impingement of high velocity flow. In comparison, lubricated plug valves must be resealed after only a few operations (high maintenance).
Failure to lubricate (grease) plug valves on a regular basis will result in valve operational problems. The cylindrical internal plug results in a reduced port, preventing pigging operations. Plug valves usually perform better with respect to throttling situations.