I'm moving over to UA for a simply reason: To keep my 100% bonus miles. As a US Gold, there is no way Im going to fly with them any more and only get 50% when I can get 100% miles with UA......easy as that!
I cleared out my US DM account and took a nice business class trip to Asia a few months ago. Now Im moving over to UA.
If I get E+ then great, if I don't then still great because Im getting almost 22,000 miles to go from London to SFO.......!