The additional frames per second you get from the faster 270X will only be a few percent over the other. It scales with the performance you are getting in the first place. For example if the RoyalQueen is giving you 60fps, the Toxic will give you 63fps if it is 5% faster. So if the RoyalQueen gives 20fps ,the Toxic will give 21fps.
Exactly how much faster the Toxic is, I don't know. But it's definitely not worth as much as an SSD.