Will $(window).resize() fire on orientation change?

the answer is imho: no

but:

$(window).on('resize orientationchange', function(){
//do stuff
});

should have you covered

careful, this can trigger twice depending on the browser

Some devices/browsers do, some not. You need to decide your supported browsers and devices.

If you want to be on secure side you should use the resize event and get/check the sizes inside in it; if you know your desired devices go with a simple orientation change:

Easy solution:

// Listen for orientation changes      
window.addEventListener("orientationchange", function() {
    // Announce the new orientation number
    alert(window.orientation);
}, false);

More secure/supported

// Listen for resize changes
window.addEventListener("resize", function() {
    // Get screen size (inner/outerWidth, inner/outerHeight)

}, false);

David Walsh wrote a good article about resize and orientation change event. More about orientation change and sizes here: http://davidwalsh.name/orientation-change