I use terra cotta and plastic for all my succulents. I have tried galvanized metal troughs for different things, but our desert sun killed almost everything I tried to grow in them. Only lavender and chives made it through! Shame because I love the look of metal containers.
For sempervivum I like terra cotta in my climate because it breathes and on hot days you can just wet the outside of the pots with water and that combined with the wind helps the plants to stay cool. Looks nice as well. Never too worried about overwatering with terra cotta because the excess just works its way to the outside of the pot and evaporates. Flip side you have to water more often. Plastic of all kinds works well too but I have to be more stingy with water. My newest ones this year I just bought some 84 cent clear plastic storage bins at Target, drilled holes in 'em, and filled them. Not very attractive but it works (budget gardening lol) and it's neat to see all the little white roots and how quickly they grow. I wish I could have mine in ground but between the hot summer sun, gophers, voles, ground squirrels, jack rabbits, etc too much of a hassle. And our "soil" here is just dusty sand (think footage from the Dust Bowl) on top of sandy clay.
terra cotta followed by plastic works best where I am. Yours look really good in the containers you have!!
