String based API vs Object based API

function onMouseOver(style) {
    size = style.getProperty("font-size");
    isize = getSizeInPoint(size);
    if (size <= 20) {
        style.setProperty("font-size", (size+1) + "pt");
    }
}

function onMouseOver(style) {
    size = style.getPropertyCSSValue("font-size");
    isize = size.getFloatValue(POINT);
    if (isize <= 20) {
        size.setFloatValue(isize+1, POINT);
    }
}