An outsider perspective here (and apologies if this is not my place to weigh in)...
I voted for Diana Taurasi as the UConn GOAT. Taurasi played on a team that was so utterly dominant in 2002 that four players were taken in the top six of the 2002 WNBA Draft. But those players graduated, and she took a team of freshmen (albeit very talented) and role players (Conlon, Valleys, Moore) to the title. Then, the next year, while Duke was loaded, while Tennessee had great players, while Texas was still a force, etc., Taurasi led them to the title.
For me, it was difficult to pick Stewart because of the constant presence of Jefferson and Tuck. Moriah is one of the two best PGs in UConn history; to me, that would be like Taurasi playing with Bird for four years. Stewart also had Stefanie Dolson and Bria Hartley for a few years, who, to me, where more accomplished than Barbara Turner and Ann Strother (in terms of what they did in college and what they went on to do after college), who were with Taurasi.
Another factor to me...if the game is tied, who is going to create and take the final shot? To me, Taurasi is one of the greatest shot creators in the history of the game.
NOW, for me the BIGGEST game-changer was the 2011 Final Four. Maya Moore had played three years with Tina Charles. Had Moore led the Huskies to the 2011 national title, I would have voted for Maya, only because she would have distinguished herself as winning a title without Charles. Maya is an amazing shot creator and a truly elite defender. That also would have given Moore three rings.
BUT let's be honest here...Moore, Stewart, and Taurasi are TITANS of the women's game. If you look at any list of BEST EVER players, all three are on it. UConn fans are very lucky to have such an embarrassment of riches that they can argue among these three as to who is the best ever player -- not just in the history of UConn, but in the history of the game. No other school can say this.