i was just forced to switch from UA (1k) to NWA and a couple things to note: 1. internationally, i feel that UA if a far superior carrier simply because of the Star Alliance opportunities, 2. SWUs that you can actually use, and 3. Real First Class. However, unless you can prove that you fly multiple hundreds of thousands of mile per year, they will only give you Premier Associate membership (below what would be called Silver Elite, but still giving you E+) with a challenge to get to Premier Exec (equal to Gold Elite). I believe the challenge is like 15k or 20k miles in 90 days or something like that, but there is zero chance they would ever match you to 1K and most likely would not let you do a challenge to 1K unless you have been a 1K in the past and want to come back.

hope this helps