i found barley straw is golden, longer stranded so you can fluff it up better whereas wheat straw is paler, shorter and flatter.
i prefer wheat straw for mucking out as it tangles less. iv never used oat straw.
barley straw is often sprayed but i cant remember if this is winter barley or spring barley, but apparently not both, its worth avoiding sprayed barley straw if using as fodder for cattle etc.