Many of the more interesting forms of content lie somewhere in between. I describe this as a spectrum, but it's not strictly one-dimensional. Nonetheless, there exists tension between the two poles. SVG occupies a fairly clear-cut niche in this spectrum. I find it rather amusing that completeness and unambiguousness can be somehow independent of the specification.
Text is represented as XML character data.
It should at least be possible for search engines to extract the text from SVG files and perform keyword searches. If SVG is successful in meeting its requirements, I believe it will satisfy an important and useful niche. However, present spec falls short in many ways. The SVG requirement has it pretty close to correct. Control over presentation implies that a conforming SVG file should display near-identically every time it's rendered.