Nothing / No one is a sure thing.
What you have and can get are prospects, many of which are better than AA at 9.
AA is like a less athletic Hendo with a jumper. Good but not great.
Give me Staus all day over AA.
Afflalo played like a borderline all star this season. He would be an upgrade at the SG position, if they wanted to continue with MKG; or they could play him at SF if the team wanted to keep Henderson in the lineup. I think him and Nelson would be good additions. It would give the team depth and proven production at the two guard positions. Is whether we go with Kemba and Afflalo, or Nelson and Henserson - whatever the combination - we'd have production that shouldn't miss a beat.
As for Afflalo versus Stauskas, the kid is talented. We'd get him for four years rather than Afflalo's two. But what it comes down to is whether the team values a proven NBA player on offense and defense, or if they want to go with a rookie. Obviously we have Henderson to start, and that would allow Stauskas can come off the bench and do what he does best. But he's not significantly more athletic than Afflalo, and he doesn't seem to be better defensively either. So while he'd probably be a cheaper option, it might be better for a team that has its heart set on becoming a better team in the East to grab the proven veteran who can still continue to improve, or at least, refine his game.
I'd go for a Nelson/Afflalo combination over Stauskas. But if we went for Stauskas in order to keep cap space free to upgrade the SF or PF position, the that could be a wise move to make. Though personally I'd go for McDermott if he's available at #9 because he can rotate with MKG, and then we can pursue one of the bigger name PFs. But that's just how I see it.