I'd say Davis by a wide margin in both redraft and dynasty. Then again, I think Davis is the most talented WR to come out of college football over the last 4 years. It hasn't clicked yet, but that doesn't mean it won't. He's only 24. He's shown flashes of becoming a guy who can take over games, its just a matter of doing it consistently. He hasn't been helped by having a new OC every year of his career, and the jury is still out on Mariota, but Davis feels like a pretty superior talent to Brown to me.
I think Brown was probably the biggest loser on draft weekend. There was a scenario where I could have justified him as high as #2 overall, but now, I think he's barely a 1st rounder. I worry that Brown will be a bit of an afterthought this year, not only behind Davis, but behind new addition Humphries, and the returning Walker.