I took UA to HNL recently, via SFO, and upgraded those legs. It was on a 777, but very different from the international ones, as Empress says. We were also upgraded from ORD to SFO, which was on a 777 continuing to Tokyo, I believe, and to get on a domestic 777 was a major step down after that. The seats are certainly better than coach, with more recline of course, but I'm not sure there is much more leg room there than in E+. If there is, the difference is marginal. I haven't done AC on that route, so I can't compare.

Of course the service is excellent, and the Mai Tai's you get after take-off are good, and so it's still pretty fun going in business, and definitely worth the extra miles. They've also re-started ice cream sundae's in domestic United.

AC business international is in my view far superior to United. Maybe the difference applies to domestic too? I wouldn't know.