The "vs." in the title of this post sets up what I believe is a false dichotomy, and suggests animosity where there ought to be solidarity. I think it's fitting, though, given the distinctions that are drawn between "classic" autism and Asperger syndrome in mainstream discourse and media. These distinctions are often based on anecdotal and pop-cultural understandings of the two diagnoses rather than on any empirical difference.
There has been disagreement among researchers and diagnosticians about whether the two diagnostic labels really represent distinct conditions since Asperger syndrome first became its own recognized and "official" diagnostic category. There are multiple sets of diagnostic criteria for Asperger syndrome, but recently the criteria put forth in the APA's Diagnostic and Statistical Manual have been thrust into the spotlight. A proposed change to the upcoming DSM V would consolidate all of the diagnoses on the autism spectrum under a single diagnostic label, "autism spectrum disorder." In popular discourse and mainstream media outlets, the other conditions on the spectrum—childhood disintegrative disorder and PDD-NOS [pervasive developmental disorder-not otherwise specified]—are completely erased. The focus is solely on "classic" autism and Asperger syndrome, and the proposed consolidation of the two labels has given rise to fierce controversy and even panic.
Since both "classic" autism and Asperger syndrome are diagnosed by observing a pattern of behavioral symptoms, rather than by identifying any physical or biological etiology, establishing an actual physiological distinction between the conditions is impossible. The DSM's current diagnostic criteria for both conditions also just don't provide for a clear distinction. The current DSM IV criteria for Asperger syndrome require that a person presents no delays in language or in overall cognitive function. However, the current criteria for autistic disorder do not conversely require that a person have language or cognitive delays. It is at the discretion of the diagnostician to determine which diagnosis is appropriate.
Personally, I am pro-consolidation for both practical and political reasons. The most recent objections to the diagnostic changes center on the hypothetical scenario of "high-functioning" people "losing" their (usually Asperger's) diagnosis because the new criteria are slightly more stringent. (A person must meet three social criteria instead of two, and exhibit two behavioral symptoms instead of one.) Lost diagnoses equal lost services, and the fear is that, somehow, people who are severely impaired enough to require support will suddenly find themselves without that support.
I can't speak to whether these fears are founded. I suspect the panic is highly premature, but what I am concerned with here are the cultural distinctions between autism and Asperger syndrome. The first wave of objections to the new diagnostic category was concerned about the connotations of the word "autism," and that concern hasn't gone away.
Asperger syndrome is often referred to as a "mild form of autism." There is no clinical or diagnostic reason to assume off-hand that a person with Asperger syndrome is less socially or behaviorally impaired than anyone else on the spectrum, yet this connotation of "mildness" persists in the popular imagination. Asperger syndrome has famously been called the "geek syndrome," and is often associated with technology-related brilliance. In popular fiction, when viewers or readers speculate as to whether or not a character is autistic, they default to the Asperger's label. No one would say that Temperance Brennan or Sherlock Holmes "has autism"—they suggest that the characters might have Asperger syndrome.
In characters who are overtly or implicitly understood to be autistic, the difference between the labels is clear in one particularly striking way. A character "with Asperger's" may be the object of sexual attraction—as in Adam, Mozart and the Whale, and The Girl With the Dragon Tattoo—but any sexuality on the part of a character "with autism" remains taboo.
"Autism" remains a scary word with extremely negative connotations. This has been offered as a reason not to merge separate diagnostic categories under the single label of "autism." The reasoning is that "higher functioning" or "mildly" impaired people should not be exposed to the stigma associated with being termed "autistic."
My biggest problem with this attitude is that it throws people who cannot avoid the "autism" label under the proverbial bus. It accepts negativity and stigma as unavoidable and even as warranted, and demurs from confronting and transforming that stigma. People from all over the spectrum already regularly refer to ourselves as "autistic" by virtue of the fact that we are "on the autism spectrum;" the designation "autistic" is definitely not currently confined to those diagnosed with "classic" autism. My hope is that merging the spectrum under a single diagnostic heading—essentially ensuring that everyone on the autism spectrum can be said to "have autism"—will strengthen solidarity among autists, and provide us further opportunity to change the way autism is perceived and represented in the popular consciousness.
Recommended for further reading:
Autism and Asperger Syndrome by Uta Frith
Asperger Syndrome edited by Ami Klin et al
Constructing Autism: Unraveling the "truth" and understanding the social by Majia Holmer Nadesan