It is all about smoothness. And you would have to ride for a while to tell. But new 105 is basically one or two generations old Ultegra. Same with Ultegra and Dura Ace. It is the same with SRAM. They all do the job some just do it smoother with less weight. 105 will work as well as Ultegra but Ultegra could feel smoother and be a few grams lighter.