As sad as it is, we will have to move one of them sooner than later. They essentially play the same role. I'm probably more in favor of trading away Scola/Mandry than Hayes - only because they will bring in better remuneration in the form of a player who can contribute. maybe a backup C for the future - or a scorer thats ready made.
I would keep both. However, if I have to choose one, it would have to be Scola. The reason is he is proven player that could be an all star in the future as he is an reigning MVP in FIBA, in spanish league and also the key player in the Argentina team. Landry also be an all star in the future and may be better than Scola but he has no track record yet (proven achievements) though he is a fantastic player last season. At this moment, Scola is my choice.