Observe these two buttons.

See how the font on the first one is dim, thin, sort of weedy-looking? And the second one is brighter, fuller?

Let’s have a look how it looks in Illustrator CS4, embiggened:

The first one is the button with the text, unchanged (11pt Arial, bold). The second one is the button with the string converted to an outline. Not that big of a difference, but when you export them, you get the above results. Why is this? What is so weird about Illustrator’s font rendering during export that makes it so different from what’s rendered on screen? It’s like the antialiasing goes into overkill and eats up too much of the text. It wouldn’t be so weird if it didn’t look different on screen before you export it.

It took a while to figure out that outline trick to make things look right again.