I can only comment on UA, but they're treating me much better as a 1K than they did when I was Premier Executive. It's not just the upgrades - they watch out for me better in other ways, too (got me on an oversold flight, protected me on a misconnect, etc.).

As for the upgrades, just try upgrading out of SFO (or any other UA hub) as a Premier Executive. But I'd say your percentages are too low - the only time I don't get the upgrade is when I have to change planes at the last minute (that is, at the airport); otherwise I'm closer to 100%. I'm also at 100% for the seven times I've stood by waiting for international upgrades with systemwide upgrades.

RichLond, your upgrade information is slightly off. All elites (any level) get a booklet with four 500-mile upgrades for every 10,000 miles they fly. In addition, 1K's get four North American upgrades, confirmable in advance, for January-March, plus two more each remaining quarter they fly at least 10,000 miles. That's 10 North American upgrades plus 6 systemwides, per year, but for 1K's only. Granted that 50-60% of my flight miles are international, but that's so many domestic upgrades I have a surplus, without buying more booklets or cashing in miles.

Bottom line: on United, 1K is far superior to Premier Executive.