XPS (Extruded Polystyrene) foam insulation boards are commonly available in 4x8-foot sheets. These sheets are used for various insulation applications in construction, such as insulating walls, roofs, and floors. XPS insulation is known for its closed-cell structure, which provides good thermal resistance and moisture resistance.
3/4" PVC sheets in a 4x8-foot size are not commonly manufactured or available in the same way as traditional plywood or other sheet goods. PVC (polyvinyl chloride) is commonly used in construction for pipes, fittings, and various other applications, but sheets of such dimensions and thickness are not as standard as they are for materials like plywood, MDF, or particleboard.