Glazed pots are sealed on the outside, so don't breathe like clay pots. In my experience, they hold moisture more than clay. Something to consider: most if not all glazed pots have only one central drain hole. Many plastic pots have several, so plastic might drain better. Overall, I think pot drainage and well-draining growing medium are the two important factors to preventing overwatering. (besides, well, watering too much
)
Have you ever tried fabric grow bags? Some gardeners swear by them.
