It would be a really hard choice for me if Anderson, Warren, and Porzingis were all available at 17. I think even at 7' Porzingis could survive defensively at SF against most or all matchups with his length, intensity, and elite agility for a 7 footer.
A Porzingis/Sullinger/KO frontcourt could be pretty freaking interesting, and Porzingis would fill out and shift to PF and Center long-term.
Sure, Porzingis would get beat and scored on off the dribble by SFs 4-5 inches shorter than him, but he wouldn't be a total disaster overall defensively on the perimeter, and he would disrupt a lot of shots on ball and off ball, and get quite a few rebounds as well.
His face up game is extremely promising, as both a shooter and as a slasher, even if he is not as ready to contribute immediately as Warren and Anderson.
http://www.youtube.com/watch?v=09v9HBG9KbI