There is a decent amount of BR's C (Royal Laurel, RL) discussions here: http://www.flyertalk.com/forum/other...rel-seats.html

I think UA F feels more exclusive, slightly bigger seats and better IFL in some US gateways. However, BR is probably better on the other fronts. Given the extra miles needed and in the spirit of trying new things, I would stick with BR RL. Bonus if you can get on the Hello Kitty Jet (through LAX or TPE-HKG)