This is good if you don't water very often - the pot will help. The pots with self watering systems are also useful if you are a lazy waterer. These pots do not assist drainage in any way. Plastic pots are bad because they heat up more in the summer - this can cause root damage and gardeners have to be very careful of where they place the darker coloured pots. High root zone temperatures stop or kill plant growth and this is definitely not what the plant doctor would recommend.
Plastic pots have the advantage of durability.
You can drop them, knock them over and grow root-bound plants in them for years and they'll survive. Cold temperatures rarely crack them and you can even get pots in any shade or colour to match your decor. The last pot in my arsenal is the clay pot. Let me make it perfectly clear - I am a devoted fan of the clay pot. Clay is porous and loses moisture faster than plastic.