Unlike FG%, "Rebounding" is not a statistic so it is hard to say. Assuming that you are looking at "what stat is most important for a team to win" and that "rebounding" is "total rebounds per game," then the answer is clear: FG%.
For 2012/3:
Top 5 FG% teams: Heat, Spurs, Thunder, Clippers, Nuggets
Top 5 teams for total rebounds: Pacers, Nuggets, Warriors, Lakers, Bucks
NBA champion Heat were dead last in rebounds per game, so how important could it be?
I haven't run the stats, but there does not seem to be much, if any, correlation, between rebounds and wins. This of course does not mean that rebounding is not important, but rather that the statistic of rebounds per game is not very important. There are advance rebounding stats like rebound rate which seem to correlate better to team success, but I don't think that was the poll question (plus it does not correlate as well to wins as FG%, based on eyeballing the date).