Clay will never be a safety
I think he'd make a very intriguing prospect as in the box safety. Teams will look at Clay and ask themselves how he can help their team. I think he has more value as a very good in the box safety than he would as a fringe OLB. The list of 220 pound LBs who become NFL starters, it's not a long list to say the least. I'm not doubting him, I just see him having a much easier path by taking the safety route.
Arthur is much more rounded than Zach. I don't see a lot of missed tackles as Kip suggests, I see some sloppy technique at times (going for the hit, not wrapping up) but this isn't an issue I've seen enough to say I'd complain about it. Zach had higher upside as an athlete to cover and the Seahawks really want guys who can move around and make plays. They're not asking the LB's (even the SAM) to rush the passer much. Arthur fits the bill perfectly for me - controlled, consistent, athletic, heart and soul of the defense type. Tremendous prospect.
I think it was the Baylor game, he had a really rough start before settling down later on. In the first two minutes of that compilation he had more missed tackles than tackles. It was embarrassing. In fairness, this kind of flaw is 100% coachable, so I seriously doubt it will deter Carroll much.
As said before, when Arthur Brown is at his best, he looks like Lavonte David, and Lavonte David is/was a really flippin' good LB. I think Pete Carroll thinks he can make Brown play at his best on a more consistent basis, so I expect him to have a very high draft grade on him. I was about as scared of Zach Brown as I was of Aaron Curry, but if Seattle drafted Arthur Brown I'd be optimistic that Pete could make it work. I just wouldn't draft him as early as Pete probably will.