Barnes was the top option as a Sophomore, Miller was the 6th man as a Senior on one of the most talented teams ever. Thats the difference. Barnes has the potential to be a top option on a team. Miller will most likely be a very reliable role player. Barnes is clearly the player with more talent and upside. Miller, however, would fit in with what the Jazz have now very well. Jazz probably won't have the option to even pick Barnes. If the Jazz don't get GS pick and find a way into the bottom of the first, Miller would be a great alternative. If the Jazz do have the GS pick and Barnes is available, you take him though (Marshall being the only alternative).
As for Perry Jones, having Jones, Evans, Milsap, Jefferson, Kanter and Favors at the 3,4, and 5... That would be awesome size. They would just need to get out on the 3, and find a way to make some on offense...