Hayward. The C's are desperate for wing scoring because quite frankly, they have none. And with the current trend in the league leaning towards more small ball, I think there should be a premium on guards and wings that can create offense/score/shoot. Hayward fits this offense like a glove, is familiar with Stevens, and the C's have a glaring hole for secondary scoring alongside IT.
Griffin is not a bad player obviously but he is older than Hayward and has a much more extensive injury history as well. Also, not convinced he's a Boston type of guy. Also, think he's likely to stay in LA as well.