The text in these two SVGs should render identically:
However the text in the first has screwed up kerning, while the text in the second doesn't. The only difference between the two SVGs is that the first one used a small font size (3px) which is scaled up by the viewBox, while the second one uses a larger font size (24px) and is not scaled. In Firebox's native SVG renderer, they both look fine.
Screenshot of the difference (as rendered on Commons):
and with render size 320px: