I flew SFO-EWR once in my entire life. I fly domestic only in conjunction with an international connection and these flights tend to be packed in my experience.

But the fact that I did get ugs on AA as a stinkin' Platinum whereas I did not as a 1K contributed to my de facto departure from UA.
I missed out on numerous GPU upgrades in my last year and had to give away 4 GPUs in January.

I recently flew UA again in coach and have to say that they are decent in coach. I understand the people who buy the cheapest ride and don't bother applying GPUs.