For Nike it will be just a background declaration, the curve with Bezier parameters and the foreground color. It will be much more compact and be able to scale.
And just as much cross-browser as CSS, which means not totally cross-browser. Your logos are broken in Opera and IE, for example.
I understand it takes much effort and expertize, but it's not the right tool for drawing images. You could do this by just exploring the UTF characters table and positioning differently colored characters near each other to make an image. But the fastest way to draw a vertored shape in a browser is still SVG.