The main thing that AR adds is global illumination, which is the ability to render bounced light and also to generate light with textures (like HDRIs) and materials. AR also adds caustics, which are reflected and transmitted light (think mirrors and prisms). There are a few other additions, but nothing too exciting there.
So, basically the reason to buy AR is global illumination. It’s most useful for architectural visualization, although it can also be very effective with product viz and other things. It wouldn’t be that useful for logo work.
You can try it out by downloading the demo.