Put simply, PVC Cable is the most common type of cable used today and consists of a chemical compound called Poly Vinyl Chloride. If a fire occurs, burning PVC Cable can emit large quantities of dense black toxic smoke, and significant amounts of hydrochloric acid.
If you have a Plenum ceiling, having PVC cable in the ceiling during a fire would cause a concentration of these fumes to be spread throughout the building. Exposure to these fumes could then hinder the safe evacuation of persons in the vicinity and result in increased fatalities. Plenum Rated Cable has a special coating on the wire, which causes it to burn at a much higher temperature and emit fewer fumes than conventional PVC. As a result, the National Electric Code (NEC) requires that only plenum rated cables be installed in plenum air spaces.
Therefore, for fire safety and code compliance concerns, choose PLENUM rated cable. If fire safety is not any concern or local code requirement, choose PVC for ease of installation and lower cost.