Salvia: Active component = Salvinorin A, which is a dissociative.
DMT and plants containing DMT: Active component = DMT (Dimethyltryptamine), which a tryptamine based psychedelic.
Psychedelics and dissociatives are a whole different series of drugs. They are both hallucinogens but they are very very different. Dissociatives switch off the senses and filters in our brain, psychedelics enhance these senses and filters.
Both have their advantages and disadvantages. The problem with Salvia is it is commonly mislabelled as a psychedelic, dissociatives are not psychedelics, they are a different hallucinogen, just as deliriants are not psychedelics. Dissociatives aren't as "ecstatic" and "enjoyable" as psychedelics, but they are very useful from an educational and spiritual point of view. If you are looking for some "fun" and you can't get psychedelics than the dissociatives DXM, PCP or Ketamine would be better choices as they have a larger effect on serotonin release than Salvia, along with a much longer duration of action. If you are looking for an educational experience, definitely choose Salvia or Ketamine as with both of these it is much easier to "break through".