The 105 is a great group set. Some call it bullet proof, but that would be an exaggeration. The Ultegra is better only in the respect of it's lighter, or so that is the most commonly held opinion. Nothing wrong with the Tiagra either for most people, me included. I have the 105 2x11 and excepting minor DR adjustments, I have not had any problems with it. Good luck, buying a new bike is always an exciting time.