Fonts looks different in Firefox and Chrome

For the ChunkFive font from FontSquirrel, specifying "font-weight: normal;" stopped Firefox's rendering from looking like ass when used in a header. Looks like Firefox was trying to apply a fake bold to a font that only has one weight, while Chrome was not.

For me, Chrome web fonts look crappy until I put the SVG font ahead of WOFF and TrueType. For example:

@font-face {
    font-family: 'source_sans_proregular';
    src: url('sourcesanspro-regular-webfont.eot');
    src: url('sourcesanspro-regular-webfont.eot?#iefix') format('embedded-opentype'),
         url('sourcesanspro-regular-webfont.svg#source_sans_proregular') format('svg'),
         url('sourcesanspro-regular-webfont.woff') format('woff'),
         url('sourcesanspro-regular-webfont.ttf') format('truetype');
    font-weight: normal;
    font-style: normal;
}

Even then, Chrome's fonts look thinner than in Firefox or IE. Chrome looks good at this point, but I usually want to set different fonts in IE and Firefox. I use a mixture of IE conditional comments and jQuery to set different fonts depending on the browser. For Firefox, I have the following function run when the page loads:

function setBrowserClasses() {
    if (true == $.browser.mozilla) {
        $('body').addClass('firefox');
    }
}

Then in my CSS, I can say

body { font-family: "source_sans_proregular", Helvetica, sans-serif; }
body.firefox { font-family: "source_sans_pro_lightregular", Helvetica, sans-serif; }

Likewise, in an IE-only stylesheet included within IE conditional comments, I can say:

body { font-family: "source_sans_pro_lightregular", Helvetica, sans-serif; }