Added B.Tate last week, but while I think he's still the best fit in my league (1pt - 50 ret. yds + TDs), I think Branch's contribution will be to make both of these guys pull-your-hair-out plays as you'll never know which of them will have a good game week-to-week. Branch is still available, but the Seahawk fan in me just can't pick him up. I think having both and deciding who to start at WR3 would drive me insane.
As far as Golden Tate vs. Deon Butler in SEA, Butler definitely has a better grasp of the offense than Tate, but he his a traditional deep-threat, where Tate is a YAC guy. Since Hasselbeck deals with jailbreaks on most plays (thanks,O-Line) the deep-ball hasn't had a place in the offense for a while. I'd go Butler for now, since he was tabbed as the most-improved player on the team going into the season, but the Seahawks offense isn't bad because of who they're starting at WR, but who they're starting on the OL.