If free domestic upgrade is most important for you, then UA would not be your choice. You are correct that 10K flown only earn 4-500 mile upgrades, and that it only comes in when you elite status. Otherwise, no 500milers earned at all. NW's free companion upgrades has no equivalent on UA, so if that is also really important to you, that might just made the decision for you.

However, if international upgrades are most important, then top tier on UA makes a lot of sense. You will get 6 SWUs, upgradeable on everything except a couple of lowest of the low buckets. Also 2 CR-1s for each 10K flown per quarter, useable on all domestic published fares.

For my base of SFO:
- 35-50K miles of upgrades by using 6 SWUs, on a mixture of Asian and Europe trips.
- 20K miles of upgrades with the eight CR-1s, on 4 transcon round trips.
- 20K worth of upgrades by the 500-milers. With 100K BIS miles, I get 40 500-miler upgrades.

That covers 75-90K of travel, and if you want to upgrade your wife/companion, then you will have to use some of your own upgrade instruments for them, reducing your own upgrade ability.