I believe that trying the suspects for the atrocious 9/11 attacks on the United States would possibly prevent grandstanding by both the suspect and their supporters. There is a slight chance that the suspect might make the trial into his own personal theater and make a mockery of the justice system but the same wasn't the case when Saddam Hussein was on trial. Although it is not the exact same example in this case (Saddam's case being outside of the U.S) the U.S. Justice system can ensure that no outbreak can come about this trial by housing it in the NYC Courts.
One objection to this idea would be to try the suspects in a place other than the NYC Courts; maybe if it's possible they should hold the trial in another court in another state so that emotions do not run high for the prosecution supporters (the U.S. people in general).
One of the great parts of the United States is the right to trial and to be confronted by your accuser. Another great right is the freedom of press. With these two rights any terrorists that wants his message conveyed to the general public will have a complete forum for doing so in trial. News Media is all to happy to take in the ratings and the terrorist is all to happy to take in the spotlight.