Simple answer is 'I don't know'. But you should bear in mind the following - which is that the advanced version of RX2 is three times the cost of Audition, and I'd say was worth it; some serious effort has gone into it and it works stunningly well. With the best will in the world, Audition's noise reduction simply isn't in that league, and it's unlikely ever to be, I'd say.
But with care, you can get exceedingly good results from Audition's NR - although you have to put quite a bit of effort, and multiple passes to do it. With RX2, you can get better results in one go - but I'd say that you really need the (expensive) Advanced version to do so. One thing that RX2 definitely does better is to deal with threshold results in a more sophisticated manner - which means that you get less issues with reverb tails, for instance.
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