The thing is that Barnes is purely an NBA 3, and he doesn't have the height, athleticism, or raw ability to be a dominant player at that position. He can be a very good player, but his ceiling seems like a Sean Elliott/Shane Battier type. Lamb, even as an NBA 2, has that wingspan where his potential ceiling is much higher. And if he gets better with his ballhandling and learns to be a scoring 1, forget about it. Little point guards wouldn't have a prayer to defend his floater. There's perhaps more risk with Lamb, but his ceiling as a backcourt player is incredibly high.