I don't think GMA is all that great of a news/entertainment program anymore --- neither is modern Today. GMA's news product feels hard to sit through as half their stories go beyond the typically hyperbole. Basically, Inside Edition Lite.
The only reason I suppose GMA is still number one is because ABC has strong local stations. The Robin/George/Lara/Josh/Sam period was strong. The addition of Strahan (however unnecessary) has as made their anchor line up even more recognizable. GMA is better at pop and out of studio segments like when they went to a school to promote Abbott elementary.
Edit: To me, GMA has stronger personalities. Michael and especially TJ have great energy. Add them to George as the hard news man and Robin who's a great bridge between the serious and light stuff.
Today however is better at news and feature stories, but it hasn't fully recovered from the Ann Curry debacle. The program has been significantly dumbed down since the fourth hour was added, even more so following Meredith and Ann's departures. Katie Couric said it herself in her biography: the hard news segments got shorter and true crime stories increasingly appeared in the 7:00 hour.