I'm going to go out on a limb and say it's Derrick Rose. Up until this year, Rose wasn't even considered the best second or third player in his position (Paul, Williams, in some circles Westbrook, Rondo). A championship win this season along with his MVP award establishes him as a legitimate superstar in the league, a privilege other members in the poll already share. Additionally, a championship win in Chicago ushers in an era of revival in the United Center not seen since Jordan, further increasing Rose's stock as a marketable figure. A title could also make it easier to attract the key piece at SG the team needs for future success.
As far as James is concerned, I think there is a real threat that a championship win could be tainted by the media because of the Heat's decision to team up together. If Wade has a better series than Lebron in the Finals, for example, winning a championship could actually hurt his legacy in the short term.
I'm not sure about that. If Lebron does win a title, the general opinion would still be "He needed Wade and Bosh to carry him to a title". That's not what I believe personally, but I feel like it's a lose-lose situation for him as far as how he's perceived on a national scale.
dirk for reasons stated. lebron will get one or more, regardless. and yes, i believe people will still talk shit about his titles. rose and durant are next. puts them at the top of the list for the nba's next best. winning now would put them there but if they win no more then they might have an average legacy.