Paul Cartledge's Spartan Reflections deals with a lot of these issues about the so-called "Spartan mirage."

Basically our sources create a huge problem with coming up with any accurate assessment of Spartan culture. First, our sources are all non-Spartans and think of Sparta essentially in terms of opposition to Sparta. This is the problem with sources like Thucydides, Plato, etc - they idealize Sparta as an answer to Athens' problems (which is basically democracy). Nor is this framed in an entirely positive way. Thucydides puts Athens and Sparta on opposite ends of the spectrum in terms of rhetoric. The Athenians are too fond of talking and sophism while the Spartans are just uneducated rubes. This is a trope that comes from Herodotus to a certain degree. His Spartans are definitely pithy, but their laconic speech also reflects a kind of simple-mindedness which is being mocked. Another issue is that our sources basically treat Spartan culture as unchanging, so sources like Pausanias, for example, create a somewhat skewed impression of Spartan life. After the Peloponnesian War, Sparta takes on a kind of Disneyland like quality with people visiting to see demonstrations of the "primitive" Spartan rites and mode of life, many characteristics of which were likely created after the war and then treated like ancient parts of the culture.

But to be more explicit in answering your question - yes some pro-oligarchic sources do paint Sparta as the superior culture (eg Plato, Xenophon). However, the Spartans were also seen as dim-witted and uneducated a quality that can be seen in works such as Herodotus and in representation of Spartans in tragedy (like Menelaus in Euripides' Helen).