I was asking this same question less than a month ago - mCX or mSR. I chose the mSR and I'm glad I did. I haven't flown an mCX, but I have seen them flown and they seem too easy to fly. I figured I would get bored with that so I purchased an mSR.
Last weekend I took my mSR to a friend's house. Three other guys flied it. One couldn't even get it to hover, but the other two hovered in their first or second battery and were moving it slowly around the room by the end of the night. One of them went on eBay and bought an mSR the next day!