I think Samberg and Kovacevic are both very intriguing prospects. I've really liked what I've seen from Samberg in games I've seen. I haven't seen Kovacevic in game action, but he really impressed me during Development Camp. His size and mobility and smarts really stood out for me in that setting. Neither of them strike me as offensive dynamos, but both of them are big, mobile D with good vision and smart puck movement.
From what I've seen at development camp I like Kovacevic's game more then Poolman's. He plays a more smooth game and imo has a bit more tools. I think he can be a very good number 5 dmen if he adapts well to the pro game.