In areas with hard water or potential for phosphate buildup I would recommend plastic. Salts will not build up in plastic as they would in clay. On the taller plants such as cymbidium, place rock shards in the bottom to weight down the pot. Also remember to flush out the salts, with whatever pot you use. Once a month or every fifth feeding use plain water.
Clay shards or granite chips are great.
These are often put into clay pots. Some of these orchids do like a bit of drying out between waterings. Hanging baskets or wooden slats are great for all kinds or or orchids with pendulous flower sprays. I use the same medium, but do have to water more often. Obviously potting Phal's in these would be silly.