Trance is the more useful of the two since Legion exists. There's really not any point in running Frostosaurus in Dinosaurs. I guess it has some use with Sea Stealth Attack, but then, with SSA, ATK is mostly irrelevant.
Not one that has any real functional significance, however. Aside from some rare circumstances involving low-ATK monsters and Enemy Controller or Canadia, which is hardly a selling point of the card, and certainly doesn't make Trance bad.