Aristotle Differentiates between Dialectician, Sophist, and Philosopher

Metaphysics Book 4 Ch 2

"[D]ialecticians and sophists assume, indeed, the same figure as the philosopher, (for sophistical is only apparent wisdom, and dialecticians dispute about all things;) to all, however, is entity common. But they dispute concerning these, evidently, from the cause of these being proper subjects of inquiry for philosophy. For, Indeed, sophistry and dialectics are employed about the same genus as philosophy is; but philosophy differs from the one in the mode of power, and from the other in the choice of life. And again, dialectic science is merely tentative of the knowledge of those things that philosophy has already actually reached; but sophistic science is only apparent, and not real. And the same is further proved by the fact that a different co-ordination of contraries is privation, and all things are referred to entity and non-entity." 

In this passage, philosophy is superior to dialectic in the "mode of power." We might take this as the superiority of "analytics" as a method and dialectic method of exploration through questioning. In a later passage, Aristotle will add that "Dialectic is merely critical where philosophy claims to know." In other words, dialectic is still struggling to understand what philosophy has already discovered.

Philosophy is superior to sophism, not because of differences in method, but because of the "choice of life," which we might take in several ways, the the exorbitant fees sophists charge, the "lifestyle" that enables, and perhaps even the tendency of sophists to move from polis to polis. Sophists have no commitment to the community, one of Plato's charges against them. This is enough for Aristotle to claim that "sophistic science is only apparent, and not real."

A final critique of both is that they claim to speak about all things. Aristotle, however, has limited philosophy to the study of essence and substance, which doesn't mean he ignores other avenues of study, only that he has characterized them, placing them in other areas of study. Dialecticians and sophists seem to be suspect because they do not recognize his categories. 

"[D]ialecticians and sophists assume the same guise as the philosopher, for sophistic is Wisdom which exists only in semblance, and dialecticians embrace all things in their dialectic, and being is common to all things, but evidently their dialectic embraces these subjects because these are proper to philosophy. For sophistic and dialectic turn on the same class of things as philosophy, but this differs from dialectic in the nature of the faculty required and from sophistic in respect of the purpose of the philosophic life. Dialectic is merely critical where philosophy claims to know, and sophistic is what appears to be philosophy but is not."