I will be honest. I have United. I spent a month in the hospital with Covid and another 4 days a few weeks later with a diabetic issue from Covid and they paid everything.
Yeah, we had United for a little while and never had issues, but then, nothing serious that we needed it for.
That said, it's a huge company and there will always be some sort of issues with policy coverage for companies as large, and profit driven as they are.