In all reality their both really similar in performance. Theres games where one is better then the other by a bit, but for most games their tied.
So it really comes down to what you find looks best, if you enjoy the look an feel of the msi gaming x then get it. Its a great card, no doubt.
Also this only applies if your looking at the 8GB version of the 480 and not the 4GB version. Because the gtx 1060 definitely has the lead over the 4GB version of the rx 480.