Im thinkin Chad Johnson will have the better fantasy yr, but Krob has more value right now. Take Krob and trade him. The reason I say this is because of the presence of D. Jackson. Jackson is still a legitimate #1 WR, not to say Krob isnt, and he will take a lot of looks away from Krob. I believe that SEA offense is gonna be good this yr, but I just have to question how much scoring is going to go to any one WR. S. Alexander will get his, but the rest have to be split, and thats not good news for fantasy owners.
Since Krob is rated so high right now, I would select him in a draft, then use his high name recognition to trade for one of the other WRs you mentioned plus somthing else.