Where are you going to after your connection? That could make quite a difference. EVA (BR) uses a lot more of their long haul planes on regional routes than ANA (NH), so it's more likely that you'd have a full lie flat seat on the connection from BR than NH.

I am in the minority on this board I think, but I don't care much for NH business class. Service is generally quite good but I'm not a fan at all of the food and their western dishes are sometimes still seafood only (regional only, you'll always get some kind of choice on long haul).

If it were myself and the connection was reasonable, I'd probably go for BR. Also of note, BR uses a 77W on this route so you know you're getting the seat you expect. NH has been known to sub in recliner 787 configuration on YVR/SEA from time to time. SEA is currently scheduled as 789 with staggered lie flat, but they recently shuffled the 788 recliner version on YVR for the coming months without advance customer notification.