Agreed that Sammy and Goodwin will be a lot more dangerous in the YAC department than Robert Woods. In a different offense I might agree with your larger point Webster, but the Bills play a run n shoot-style passing game, the key principle being attacking downfield in numbers. Using the outside receivers to force the safeties away from the middle of the field, opening deep routes between the hashes for the slot man. Andre Reed, Marques Colston (under Marrone himself) and Victor Cruz are examples of downfield threats who've thrived in the slot in related systems. I think Woods is a decent fit because he can do some of the Welker-style traditional slot stuff, and can attack down the field.
FWIW I think the ultimate long-term goal now that we have a player like Watkins (talking years down the road) will be to set up our personnel in a way that allows Watkins to play the slot full-time, in other words to be the Andre Reed of this offense. Right now using him more on the outside and allowing Woods to make plays in the middle is the best way to get full value out of Woods and by extension the WR core at large.