Clay pots dry out quicker than plastic ones. They also allow fresh air to diffuse into the root zone. Soil remains somewhat cooler in clay pots due both to insulation and evaporation through the clay. More rapid growth of succulents can occur in plastic pots due to the root temperature differential. Better aeration can be achieved by adding perlite to plastic pots than by using clay pots alone.
Plastic pots require much less labor in the form of watering.
Some succulents which are difficult to grow do best in clay pots with abundant perlite and sterilized soil. Watering Most cacti and other succulents thrive with ample intermittent watering. The top one-half inch of soil should be completely dry before rewatering. Although succulents will tolerate periodic drought, most need ample periodic rain or artificial watering. Most cacti in Arizona grow in microhabitats that receive periodic but ample seepage or run-off following rains.