I'd stay with UA since you'll be able to use your systemwide upgrades and/or miles you've already acccumulated. If you switch, those SWU's would expire and you'd have to fly for awhile to be able to use accumulated miles in the new program for upgrades. Also, some airline programs won't status match you to their highest tiers even if you are a 1K. As we always like say around here, YMMV.