I just went through my records and am 17/28 for complimentary upgrades on domestic flights this year and 3/28 for accepting a paid upgrade offer (of typically $109) at checkin for a total of 20/28 flights flown in F and 8 flown in Y on purchased coach fares on United as a 1K flying out of Houston in 2016. I also have quite a few paid F flights and a few regional flights on ERJ-145s but didn't include those in the numbers.

I can't believe UA is giving more complimentary upgrades than DL at this point, but I have had very good luck since UA raised the premium for purchased F fares early in the year.