The 25' is not only longer, it's wider, has larger tanks, bigger brakes, bigger tires, more seating, and more open. You will love it. If you consider tow vehicle, trailer, people, gear and supplies as a total weight, the 25' is not much difference from the 23'. The 2012 models have some nice upgrades.
I am unfamiliar with the Trailblazer and whether it is enough for either trailer. You made a good choice on the trailer. Get some professional help setting up your tow vehicle, if determined adequate.