It all depends on your taste and growing conditions, really. Here in Arkansas, I would not grow a phal on a mount because it would dry out way to fast in our summer heat. They do well for us potted in smaller bark mix. I have seen some mounted phals at shows that are just stunning, though. Those usually have the inflorescence hanging down as they would in nature. I really like the way they look, but I just do better with orchids in pots. My catts and phrags and paphs are the easiest for me. - all in pots.
Cheers,
BD