Carnival Liberty or Carnival Glory?

Thinking about taking a Carnival cruise vacation in January 2012. We are thinking about either the Carnival Liberty or the Carnival Glory. The Liberty goes to Isla Roatan, Cozumel, Grand Cayman, and Belize (Western Caribbean), and the Glory goes to St. Thomas, San Juan, Nassau, and Grand Turk. Which itinerary do you think is better? Which ship is better?Which cruise should we go on? I'm a single mom with a 13 year old daughter if that helps.